Chapter 2 OpenStax Atoms, Molecules, Ions. .

acids are what compound

ionic compound but when the ionize their hydrogen ions (loan proton) become the cation and the rest of parts become the anion HCLO3----- H+ + CLO3- HF-------- H+ + F- H2S-------- 2H+ + s 2- (must balance anions and cations to cancel each other charges out)

isotope

isotopes—atoms of the same element that differ in mass

metals nonmetals metalloids

metals (elements that are shiny, malleable, good conductors of heat and electricity—shaded yellow); nonmetals (elements that appear dull, poor conductors of heat and electricity—shaded green); and metalloids (elements that conduct heat and electricity moderately well, and possess some properties of metals and some properties of nonmetals—shaded purple).

molecular formula

molecular formula is a representation of a molecule that uses chemical symbols to indicate the types of atoms followed by subscripts to show the number of atoms of each type in the molecule. (A subscript is used only when more than one atom of a given type is present.) Molecular formulas are also used as abbreviations for the names of compounds.

Naturally occurring copper consists of 63Cu (mass 62.9296 amu) and 65Cu (mass 64.9278 amu), with an average mass of 63.546 amu. What is the percent composition of Cu in terms of these two isotopes?

Answer: 69.15% Cu-63 and 30.85% Cu-6 .

Atoms of each of the following elements are essential for life. Give the group name for the following elements: (a) chlorine (b) calcium (c) sodium (d) sulfur

The family names are as follows: (a) halogen (b) alkaline earth metal (c) alkali metal (d) chalcoge

molecular compound

These molecular compounds (covalent compounds) result when atoms share, rather than transfer (gain or lose), electrons usually formed by a combination of nonmetals. Thus ,the periodic table can help us recognize many of the compounds that are covalent.

.Analysis of a sample of the gass howed that it consisted of 91.84% 20Ne (mass 19.9924 amu), 0.47% 21Ne (mass 20.9940 amu), and 7.69% 22Ne (mass 21.9914 amu). What is the average mass of the neon in the solar wind?

average mass =(0.9184×19.9924 amu)+(0.0047×20.9940 amu)+(0.0769×21.9914 amu) =(18.36+0.099+1.69)amu =20.15 amu

empirical and molecular formula for benzene contains two elements, carbon(C)and hydrogen(H)

benzene contains two elements, carbon(C)and hydrogen(H) ,and that for every carbon atom in benzene ,there is one hydrogen atom. Thus, the empirical formula is CH. An experimental determination of the molecular mass reveals that a molecule of benzene contains six carbon atoms and six hydrogen atoms, so the molecular formula for benzene is C6H6

1. binary compound

binary compounds, those containing only two elements, The name of a binary compound containing monatomic ions consists of the name of the cation(the name of the metal) followed by the name of the anion

the element boron is composed of two isotopes: About 19.9% of all boron atoms are 10B with a mass of 10.0129 amu, and the remaining 80.1% are 11B with a mass of 11.0093 amu. The average atomic mass for boron is calculated to be:

boron average mass =(0.199×10.0129 amu)+(0.801×11.0093 amu) =1.99 amu+8.82 amu =10.81 amu

periodic law

the properties of the elements are periodic functions of their atomic numbers.

proton

the proton, the positively charged, subatomic particle found in the nucleus

molecular formula

we can describe a compound with a molecular formula, in which the subscripts indicate the actual numbers of atoms of each element in a molecule of the compound

(a) KI, the compound used as a source of iodine in table salt (b) H2O2, the bleach and disinfectant hydrogen peroxide (c) CHCl3, the anesthetic chloroform (d) Li2CO3, a source of lithium in antidepressants

(a) Potassium (group 1) is a metal, and iodine (group 17) is a nonmetal; KI is predicted to be ionic. (b) Hydrogen (group 1) is a nonmetal, and oxygen (group 16) is a nonmetal; H2O2 is predicted to be molecular (c) Carbon (group 14) is a nonmetal, hydrogen (group 1) is a nonmetal, and chlorine (group 17) is a nonmetal; CHCl3 is predicted to be molecular. (d) Lithium (group 1A) is a metal, and carbonate is a polyatomic ion; Li2CO3 is predicted to be ionic.

Predicting the Type of Bonding in Compounds Predict whether the following compounds are ionic or molecular: (a) KI, the compound used as a source of iodine in table salt (b) H2O2, the bleach and disinfectant hydrogen peroxide (c) CHCl3, the anesthetic chloroform (d) Li2CO3, a source of lithium in antidepressant

(a) Potassium (group 1) is a metal, and iodine (group 17) is a nonmetal; KI is predicted to be ionic. (b) Hydrogen (group 1) is a nonmetal, and oxygen (group 16) is a nonmetal; H2O2 is predicted to be molecular. (c) Carbon (group 14) is a nonmetal, hydrogen (group 1) is a nonmetal, and chlorine (group 17) is a nonmetal; CHCl3 is predicted to be molecular. (d) Lithium (group 1A) is a metal, and carbonate is a polyatomic ion; Li2CO3 is predicted to be ionic.

Name the following ionic compounds, which contain a metal that can have more than one ionic charge: (a) Fe2S3 (b) CuSe (c) GaN (d) CrCl3 (e) Ti2(SO4)3

(a) iron(III) sulfide (b) copper(II) selenide (c) gallium(III) nitride (d) chromium(III) chloride (e) titanium(III) sulfate

Naming Ionic Compounds Name the following ionic compounds, which contain a metal that can have more than one ionic charge: (a) Fe2S3 (b) CuSe (c) GaN (d) CrCl3 (e) Ti2(SO4)3

(a) iron(III) sulfide (b) copper(II) selenide (c) gallium(III) nitride (d) chromium(III) chloride (e) titanium(III) sulfate

Give the group name for each of the following elements: (a) krypton (b) selenium (c) barium (d) lithium

(a) noble gas; (b) chalcogen; (c) alkaline earth metal; (d) alkali metal

Transitional group

(hard to predict what they are going to do with how many electrons going to take or give) the namine becomes harder for them 1. write the name of the transional metal 2. use roman numerals to denote size of ion charge

Ionic Compounds

(have both cations and anions) 1. list cation first than anion

naming monatomic ions

- form with single atom 1. use chemical symbol 2. add charge as subscript (any charge greater than 2 gets the number with it)

7. Binary Acids

-Some compounds containing hydrogen are members of an important class of substances known as acids. -that many acids release hydrogen ions, H+, when dissolved in water - binary acid (comprised of hydrogen and one other nonmetallic element) 1. The word "hydrogen" is changed to the prefix hydro 2. The other nonmetallic element name is modified by adding the suffix -ic 3. The word "acid" is added as a second word

Note that there is a system for naming some polyatomic ions -ate/-ite per-/ hypo-

-ate and -ite are suffixes designating polyatomic ions containing more or fewer oxygen atoms. Per- (short for "hyper") and hypo- (meaning "under") are prefixes meaning more oxygen atoms than -ate and fewer oxygen atoms than -ite, respectively.

8. Oxyacids

-compounds that contain hydrogen, oxygen, and at least one other element, and are bonded in such a way as to impart acidic properties to the compound To name oxyacids: 1. Omit "hydrogen" 2. Start with the root name of the anion 3. Replace -ate with -ic, or -ite with -ous 4. Add "acid"

draw periodic table page 104

.

Here are the postulates of Dalton's atomic theory

. Matter is composed of exceedingly small particles called atoms. An atom is the smallest unit of an element that can participate in a chemical change. An element consists of only one type ofatom, which has a mass thatis characteristic ofthe element and is the same for all atoms of that element

Ca3(PO4)2

. We use parentheses in a formula to indicate a group of atoms that behave as a unit. For example, the formula for calcium phosphate, one of the minerals in our bones, is Ca3(PO4)2. This formula indicates that there are three calcium ions(Ca2+)forevery twophosphate (PO43−) groups.

questions we need to ask ourselves about the compounds before we name them

.First, is the compound ionic or molecular? If the compound is ionic, does the metal form ions of only one type (fixed charge) or more than one type (variable charge)?Aretheionsmonatomicorpolyatomic?Ifthecompoundismolecular,doesitcontainhydrogen?If so, does it also contain oxygen?

group 2

.Theelementsingroup2(thesecondcolumn)form compounds consisting of one atom of the element and two atoms of hydrogen: These are called alkaline earth metals, with similar properties among members of that group.

covalent bonds

.When electrons are"shared" and molecules form, covalent bonds result. Covalent bonds are the attractive forces between the positively charged nuclei of the bonded atoms and one or more pairs of electrons that are located between the atoms.

Nomenclature Prefixes

1 (sometimes omitted) mono- 6 hexa 2 di- 7 hepta 3 tri- 8 octa 4 tetra- 9 nona 5 penta- 10 deca

Rutherford drew two conclusions:

1. The volume occupied by an atom must consist of a large amount of empty space. 2. A small, relatively heavy, positively charged body, the nucleus, must be at the center of each atom.

Two Types of acids 1. acids without oxygen 2. acids with oxygen

1. break apart (separate H+ and anion) 2. make sure + and - balance out 3. figure out the name of the anion 4. if ends with "idle" than put the word into hydro____ ic acid ex: HCL H+ + Cl- chloride hydrochloric acid ex: HBr H+ + Br- bromide hydrobromic acid

elements from the left and elements from the right what do they form and what names are they typically

1. left (alkaline/alkaline earth metals)- lose electrons= form cations (end with "ion") 2. right (halogens, etc)- gain electrons= form anions (end with "ide")

naming anions

1. write the name of the element 2. follow with ide

Naming cations

1. write the name of the element 2. follow work with ion

A sample of compound X (a clear, colorless, combustible liquid with a noticeable odor) is analyzed and found to contain 14.13 g carbon and 2.96 g hydrogen. A sample of compound Y (a clear, colorless, combustible liquid with a noticeable odor that is slightly different from X's odor) is analyzed and found to contain 19.91 g carbon and 3.34 g hydrogen. Are these data an example of the law of definite proportions, the law of multiple proportions, or neither? What do these data tell you about substances X and Y?

14.13C/ 2.96 = 4.77/1 19.91 C/ 3.34 H = 5.96/1 4.77/ 5.96 = .800= 4/5 This small, whole-number ratio supports the law of multiple

groups

18 vertical columns, called groups

An atom of platinum has a mass number of 195 a nd contains 74 electrons. How many protons and neutrons does it contain, and what is its charge?

195 atomic # 78 neutrons 117 electrons 74 +4 charge

Naturally occurring chlorine consists of 35Cl(mass34.96885amu)and 37Cl(mass36.96590amu),withan average mass of 35.453 amu. What is the percent composition of Cl in terms of these two isotopes?

35.453 amu = (x×34.96885 amu)+[(1.00−x)×36.96590 amu] 35.453 = 34.96885x+36.96590−36.96590x 1.99705x = 1.513 x = 1.513 1.99705 =0.7576

A molecule of metaldehyde (a pesticide used for snails and slugs) contains 8 carbon atoms, 16 hydrogen atoms, and 4 oxygen atoms. What are the molecular and empirical formulas of metaldehyde?

8:16:4 /4 2:4:1 Molecular formula, C8H16O4; empirical formula, C2H4O

predicating ion compounds

A compound that contains ions and is held together by ionic bonds is called an ionic compound. The periodic table can help us recognize many of the compounds that are ionic: When a metalis combined with one or more nonmetals, the compound is usually ionic. This guideline works well for predicting ionic compound formation for most of the compounds typically encountered in an introductory chemistry course. However, it is not always true

diagram page 95

A methane molecule can be represented as (a) a molecular formula, (b) a structural formula, (c) a balland-stick model, and (d) a space-filling model. Carbon and hydrogen atoms are represented by black and white spheres, respectively.

neutral atom

A neutral atom must contain the same number of positive and negative charges, so the number of protons equals the number of electrons

Aluminum and carbon react to form an ionic compound. Predict which forms an anion, which forms a cation, and the charges of each ion. Write the symbol for each ion and name them.

Al will form a cation with a charge of 3+: Al3+, an aluminum ion. Carbon will form an anion with a charge of 4−: C4−, a carbide ion

diatomic molecules

Although many elements consist of discrete, individual atoms, some exist as molecules made up of two or more atoms of the element chemically bonded together. For example, most samples of the elements hydrogen, oxygen, and nitrogen are composed of molecules that contain two atoms each (called diatomic molecules) and thus have the molecularformulasH2,O2,andN2,respectively

anion

An atom that gains one or more electrons will exhibit a negative charge and is called an anion.

cation

An atom that gains one or more electrons will exhibit a negative charge and is called an anion.

Write the formulas for the following compounds: (a) phosphorus pentachloride (b) dinitrogen monoxide (c) iodine heptafluoride (d) carbon tetrachlorid

Answer: (a) PCl5; (b) N2O; (c) IF7; (d) CCl

Using the periodic table, predict whether the following compounds are ionic or covalent (a) SO2 (b) CaF2 (c) N2H4 (d) Al2(SO4)3

Answer: (a) molecular; (b) ionic; (c) molecular; (d) ioni

A sample of magnesium is found to contain 78.70% of 24Mg atoms (mass 23.98 amu), 10.13% of 25Mg atoms (mass 24.99 amu), and 11.17% of 26Mg atoms (mass 25.98 amu). Calculate the average mass of a Mg atom.

Answer: 24.31 amu

Predict the formula of the ionic compound formed between the lithium ion and the peroxide ion, O22− (Hint: Use the periodic table to predict the sign and the charge on the lithium ion.)

Answer: Li2O2

what happens to metals: gain/lose electrons normally

Atoms of many main-group metals lose enough electrons to leave them with the same number of electrons as an atom of the preceding noble gas

mass number

Because each proton and each neutron contribute approximately one amu to the mass of an atom, and each electron contributes far less, the atomic mass of a single atom is approximately equal to its mass number (a whole number). However, the average masses of atom s of most elements are not whole numbers because most elements exist naturally as mixtures of two or more isotopes. atomic masses is a weighted, average mass of all the isotopes present in a naturally occurring sample of that element. This is equal to the sum of each individual isotope's mass multiplied by its fractional abundance. average mass =∑ i (fractional abundance×isotopic mass)i

The gemstone sapphire (Figure 2.31) is mostly a compound of aluminum and oxygen that contains aluminum cations, Al3+, and oxygen anions, O2−. What is the formula of this compound?

Because the ionic compound must be electrically neutral, it must have the same number of positive and negative charges. Two aluminum ions, each with a charge of 3+, would give us six positive charges, and threeoxideions,eachwithachargeof2−, wouldgiveussixnegativecharges.T heformulawouldbe Al2O3.

The gemstone sapphire (Figure 2.31) is mostly a compound of aluminum and oxygen that contains aluminum cations, Al3+, and oxygen anions, O2−. What is the formula of this compound?

Because the ionic compound must be electrically neutral, it must have the same number of positive and negative charges. Two aluminum ions, each with a charge of 3+, would give us six positive charges, and threeoxideions,eachwithachargeof2−, would give us six negative charges. TheformulawouldbeAl2O3.

An ion found in some compounds used as antiperspirants contains 13 protons and 10 electrons. What is its symbol?

Because the number of protons remains unchanged when an atom forms an ion, the atomic number of the element must be 13. Knowing this lets us use the periodic table to identify the element as Al (aluminum). TheAlatomhaslostthreeelectronsandthushasthreemorepositivecharges(13)thanithaselectrons(10). This is the aluminum cation, Al3+.

Naming Covalent Compounds Name the following covalent compounds: (a) SF6 (b) N2O3 (c) Cl2O7 (d) P4O6

Because these compounds consist solely of nonmetals, we use prefixes to designate the number of atoms of each element: (a) sulfur hexafluoride (b) dinitrogen trioxide (c) dichlorine heptoxide (d) tetraphosphorus hexoxide

Name the following covalent compounds: (a) SF6 (b) N2O3 (c) Cl2O7 (d) P4O6

Becausethesecompoundsconsistsolely ofnonmetals,weuseprefixestodesignatethenumber ofatomsof each element: (a) sulfur hexafluoride (b) dinitrogen trioxide (c) dichlorine heptoxide (d) tetraphosphorus hexoxide

compounds are formed

Compounds are formed when two or more elements chemically combine, resulting in the formation of bonds. For example, hydrogen and oxygen can react to form water, and sodium and chlorine can react to form table salt.

2, Compounds Polyatomic Ions

Compounds containing polyatomic ions are named similarly to those containing only monatomic ions, except there is no need to change to an-ide ending, since the suffix is already present in the name of the anion

Compounds Containing Polyatomic Ions

Compounds containing polyatomic ions are named similarly to those containing only mon atomic ions ,except there is no need to change to an-ideending, since the suffix is already present in the name of the anion

For example, consider H2CO3

For example, consider H2CO3 (which you might be tempted to call "hydrogen carbonate"). To name this correctly, "hydrogen" is omitted; the -ate of carbonate is replace with -ic; and acid is added—so its name is carbonic acid

Na+ and C2O42−

However, the formulas for some ionic compounds containing polyatomic ions are not empirical formulas. For example, the ionic compound sodium oxalate is comprised of Na+ and C2O42− ions combined in a 2:1 ratio, and its formula is written as Na2C2O4. The subscripts in this formula aren ot the smallest-possible whole numbers, as each can be divided by 2 to yield the empirical formula, NaCO2. This is not the accepted formula for sodiumoxalate, however, as it does not accurately represent the compound's polyatomic anion, C2O42−.

questions to ask to figure out what to name compounds

If the compound is ionic, does the metal form ions of only one type (fixed charge) or more than one type (variablecharge)?Aretheionsmonatomicorpolyatomic?Ifthecompoundismolecular,doesitcontainhydrogen?If so, does it also contain oxygen? From the answers we derive, we place the compound in an appropriate category and then name it accordingly.

charge of ionic compound

In every ionic compound, the total number of positive charges of the cations equals the total number of negative charges of the anions. Thus, ionic compounds are electrically neutral overall, even though they contain positive and negativeions

ionic compounds properties

Ionic compounds are solids that typically melt at high temperatures and boil at even higher temperatures. In solid form, an ionic compound is not electrically conductive because its ions are unable to flow .When molten,however ,it can conduct electricity because its ions are able to move freely through the liquid

H2 2H 2H2

It is important to note that a subscript following a symbol and a number in front of a symbol do not represent the same thing; for example, H2 and 2H represent distinctly different species. H2 is a molecular formula; it represents a diatomic molecule of hydrogen, consisting of two atoms of the element that are chemically bonded together. The expression 2H, on the other hand, indicates two separate hydrogen atoms that are not combined as a unit. The expression 2H2 represents two molecules of diatomic hydrogen

Predict the formula of the ionic compound formed between the lithium ion and the peroxide ion, O2 2− (Hint: Use the periodic table to predict the sign and the charge on the lithium ion.)

Li- alakine metal (gives an electron, 1+ charge) 2Lio2

3. Compounds Containing a Metal Ion with a Variable Charge

Most of the transition metals can form two or more cations with different charges. Compounds of these metals with nonmetals are named with the same method as compounds in the first category, except the charge of the metal ion is specified by a Roman numeral in parentheses after the name of the metal

Compounds Containing a Metal Ion with a Variable Charge

Most of the transition metals can form two or more cations with different charges. Compounds of these metals with nonmetals are named with the same method as compounds in the first category, except the charge of the metal ion is specified by a Roman numeral in parentheses after the name of the metal. The charge of the metal ion is determined from the formula of the compound and the charge of the anion.

moving from right to left

Moving from the far right to the left on the periodic table, elements often form anions with a negative charge equal to the number of groupsmovedleftfromthenoblegases.Forexample, group17elements (onegroupleftofthenoblegases)form1− ions; group 16 elements (two groups left) form 2− ions, and so on

mnemonic

My r"ide" has "hydro" l "ics I "ate" something "ic"ky spr "ite" is delic "ious"

example: take any two compounds (double element each compound) and with the atomic mass numbers and finding the ratio you will end up with a whole number. this supported the fact that there are atoms)

NO2= n/o= 1/2= 14/(16X2) 32 = .44/1 NO4= n/o= 1/4= 14/ (16X4) 64 = .22/1 .44/.22 = 2

Predict the formula of the ionic compound formed between the sodium cation, Na+, and the sulfide anion, S2−

Na2 S

Predict the formula of the ionic compound formed between the sodium cation, Na+, and the sulfide anion, S2−.

Na2S

nomenclature

Nomenclature, a collection of rules for naming things, is important in science and in many other situations

groups 15 16 17 18 (names)

Other groups with specific names are the pnictogens (group 15), chalcogens(group16), halogens(group17),andthe noble gases (group18,alsoknownasinertgases).

4. Out-of-date nomenclature used the suffixes

Out-of-date nomenclature used the suffixes -ic and -ous to designate metals with higher and lower charges, respectively: Iron(III)chloride, FeCl3,waspreviously called ferric chloride, andiron(II)chloride, FeCl2,wasknown as ferrous chloride.

Oxyanions

Oxyanions are polyatomicions that contain one or more oxygen atoms

Give the symbol and name for the ion with 34 protons and 36 electrons

Se2−, the selenide ion

moving from left to right

That is, group 1 elements form 1+ ions; group 2 elements form 2+ ions, and so on

atomic mass unit (amu)

The AMU is used to express the relative masses of, and thereby differentiate between, various isotopes of elements. Thus, for example, uranium-235 (U-235) has an AMU of approximately 235, while uranium-238 (U-238) is slightly more massive. The difference results from the fact that U-238, the most abundant naturally occurring isotope of uranium, has three more neutrons than U-235, an isotope that has been used in nuclear reactors and atomic bombs. Atomic mass is the sum of all the protons, neutrons, and electrons in a single atom or molecule.[1] The mass of an electron is so small, it is considered negligible and not included in the calculation

The Number of Electrons is...

The Number of Electrons is... By definition, atoms have no overall electrical charge. That means that there must be a balance between the positively charged protons and the negatively charged electrons. Atoms must have equal numbers of protons and electrons.

Molecular (Covalent) Compounds

The bonding characteristics of inorganic molecular compounds are different from ionic compounds, and they are named using a different system as well. The charges of cations and anions dictate their ratios in ionic compounds, so specifying the names of the ions provides sufficient information to determine chemical formulas. However, because covalent bonding allows for significant variation in the combination ratios of the atoms in a molecule, the names for molecular compounds must explicitly identify these ratios

5. Molecular (Covalent) Compound

The charges of cations and anions dictate their ratios in ionic compounds, so specifying the names of the ions provides sufficient information to determine chemical formulas

periods or series

The elements are arranged in seven horizontal rows

Molecules of glucose (blood sugar)contain6carbonatoms,12hydrogenatoms,and6oxygenatoms.What are the molecular and empirical formulas of glucose

The molecular formula is C6H12O6 because one molecule actually contains 6 C, 12 H, and 6 O atoms. The simplest whole-number ratio of C to H to O atoms in glucose is 1:2:1, so the empirical formula is CH2O

Compounds Containing Only Monatomic Ions

The name of abinary compound containing monatomic ions consists of the name ofthe cation(thenameof the metal) followed by the name of the anion (the name of the nonmetallic element with its ending replaced by the suffix -ide

atomic number(Z)

The number of protons in the nucleus of an atom is it atomic number(Z) This is the defining trait of an element: Its value determines the identity of the atom. For example, any atom that contains six protons is the element carbon and has the atomic number 6, regardless of how many neutrons or electrons it may have

J. J. Thomson produced a visible beam in a cathode ray tube what did he find out

The particles are attracted by positive (+) charges and repelled by negative (−) charges, so they must be negatively charged (like charges repel and unlike charges attract); they are less massive than atoms and indistinguishable, regardless of the source material, so they must be fundamental, subatomic constituents of all atoms.

Bakingpowdercontains calcium dihydrogen phosphate ,an ionic compound composed of the ions Ca2+ and H2PO4−. What is the formula of this compound?

The positive and negative charges must balance, and this ionic compound must be electrically neutral.Thus, wemusthavetwonegativechargestobalancethe2+charge ofthe calcium ion. This requires a ratio of one Ca2+ ion to two H2PO4− ions. We designate this by enclosing the formula for the dihydrogen phosphate ion in parentheses and adding a subscript 2. The formula is Ca(H2PO4)2.

Magnesium and nitrogen react to form an ionic compound. Predict which forms an anion, which forms a cation, and the charges of each ion. Write the symbol for each ion and name them

The symbol for the ion is Mg2+, and it is called a magnesium ion The symbol for the ion is N3−, and it is called a nitride ion

mass number

The total number of protons and neutrons in an atom is called its mass number (A).

form compounds

The transfer and sharing of electrons among atoms govern the chemistry of the elements. During the formation of some compounds, atoms gain or lose electrons, and form electrically charged particles called ions

example of isotopes

These isotopes can be identified as 24Mg, 25Mg, and 26Mg. These isotope symbols are read as "element, mass number" and can be symbolized consistent with this reading. For instance, 24Mg is read as "magnesium 24," and can be written as "magnesium-24" or "Mg-24." 25Mg is read as "magnesium 25," and can be written as "magnesium-25" or "Mg-25." All magnesium atoms have 12 protons in their nucleus. They differ only because a 24Mg atom has 12 neutrons in its nucleus, a 25Mg atom has 13 neutrons, and a 26Mg has 14 neutrons

molecular compound

These molecular compounds (covalent compounds) result when atoms share, rather than transfer (gain or lose), electrons.

For example, the molecular formula for acetic acid, the component that gives vinegar its sharp taste, is C2H4O2 what is the empirical

This formula indicates that a molecule of acetic acid (Figure 2.21) contains two carbon atoms, four hydrogen atoms, and two oxygen atoms. The ratio of atoms is 2:4:2. Dividing by the lowest common denominator (2) gives the simplest, whole-number ratio of atoms, 1:2:1, so the empirical formula is CH2O. Note that a molecular formula is always a whole-number multiple of an empirical formula.

ionic bonds

When an element composed of atoms that readily lose electrons (a metal) reacts with an element composed of atoms that readily gain electrons(anonmetal), atransfer of electrons usually occurs,producingions.Thecompoundformed by this transfer is stabilized by the electrostatic attractions (ionic bonds) between the ions of opposite charge present in the compound.

what happens to nonmetals: gain/lose electrons normally

When atoms of nonmetal elements form ions, they generally gain enough electrons to give them the same number of electronsasanatomofthenextnoblegasintheperiodictable

ionic bonds

When electrons are transferred and ions form, ionic bonds result. Ionic bonds are electrostatic forces of attraction ,that is ,the attractive forces experienced between objects of opposite electrical charge

ion charge of an atom is defined as follows

When the numbers ofthese subatomic particles are not equal, the atom is electrically charged and is called an ion. The charge of an atom is defined as follows: Atomic charge = number of protons − number of electron

Compounds Composed of Two Elements

When two nonmetallic elements form a molecular compound, several combination ratios are often possible. For example, carbon and oxygen can form the compounds COandCO2. Since these are different substances with different properties, they cannot both have the same name(they cannot both be called carbonoxide).To deal with this situation, we use a naming method that is some what similar t o that usedfor ionic compounds, but with added prefixe s to specify the numbers of atoms of each element.

electron

a negatively charged, subatomic particle with a mass more than one thousand-times less that of an atom

2. acids with oxygen

acids with oxygen have polyatomic ions (oxygens that combine with other elemts) (this group has a charge - and ends with either an ate or ite) 1. break up with H+ and anion 2. look at anions name 3. if ends with ate take off and add ic 4. if ends with ite than add ous to the end ex: H2Co3 2H+ + Co3 -2 (blance out) carbonate carbonic acid HN0 2 ---- H + + No2 - nitrite nitrious

group 1 and group 2 predict what cation/anion and how many electrons gain/lost

an atom of an alkali metal (group 1) loses one electron and forms a cation with a 1+ charge; an alkaline earth metal (group 2) loses two electrons and forms a cation with a 2+ charge, and so on.

chemical symbol

chemical symbol is an abbreviation that we use to indicate an element or an atom of an element. For example, the symbol for mercury is Hg

covalent compounds are formed with how to use the periodic table to tell what compounds are ionic or covalent.

covalent compounds are usually formed by a combination of nonmetals. Thus, the periodic table can help us recognize many of the compounds that are covalent. While we can use the positions of a compound's elements in the periodic table to predict whether it is ionic or covalent at this point in our study of chemistry, yous hould be aware that this is a very simplistic approach that does not account for a number of interesting exceptions.

isotope

each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.

empirical formula,

empirical formula, which indicates the types of atoms present and the simplest whole-number ratio of the number of atoms (or ions) in the compound

6. Compounds Composed of Two Elements

example: ,carbon and oxygen can form the compounds CO and CO2 Since these are different substances with different properties, they cannot both have the same name (they cannot both be called carbonoxide) .To deal with this situation, we use a naming method that is some what similar to that used for ionic compounds, but with added prefixes to specify the numbers of atoms of each element

law of conservation of mater

if an element such as copper consists of only one kind of atom, then it cannot be broken down into simpler substances, that is, into substances composed of fewer types of atoms. And if atoms are neither created nor destroyed during a chemical change, then the total mass of matter present when matter changes from one type to another will remain constant This violates Dalton's postulate that atoms are neither created nor destroyed during a chemical change, but are merely redistributed

isomers

isomers—compounds with the same chemical formula but different molecular structures Note that this small difference in the arrangement of the atoms has a major effect on their respective chemical properties. You would certainly not want to use a solution of methyl formate as a substitute for a solution of acetic acid (vinegar) when you make salad dressing

how neutrons explain isotopes

isotopes- They differ in mass because they have different numbers of neutrons, but they are chemically identical because they have the same number of protons.

The iodine atoms are added as anions, and each has a 1− charge and a mass number of 127. Determine the numbers of protons, neutrons, and electrons in one of these iodine anions.

mass # 127 1- charge Atomic number= 53 74 neutrons 54 electrons

molecular compound

molecular compounds (covalent compounds) result when atoms share, rather than transfer (gain or lose), electrons. covalent compounds are usually formed by acombination of nonmetals. Thus, the periodic table can help us recognize many of the compounds that are covalent. While we can use the positions of ac ompound's elements in the periodic table to predict whether it is ionic or covalent at this point in our study of chemistry, you should be aware that this is a very simplistic approach thatdoes not account for a number of interesting exceptions.

molecular compound properties

molecular compounds often exist as gases, low-boiling liquids, and low-melting solids, although many important exceptions exist.

monatomic ions polyatomic ions.

monatomic ions, that is, they are ions formed from only one atom. polyatomic ions. These ions, which act as discrete units, are electrically charged molecules (a groupofbondedatomswithanoverallcharge

negative ions/ acids

negative ions / acids -ide hydro______ ic -ate -ic acid -ite -ous acid

neutrons

nucleus was known to contain almost all of the mass of an atom, with the number of protons only providing half, or less, of that mass. this lead to the discovery of neutrons. neutrons, uncharged, subatomic particles with a mass approximately the same as that of protons.

The symbols H, 2H, H2, and 2H2 represent very different entitie

page 96 diagram .

periodic table arranges the elements in increasing

periodic table arranges the elements in increasing order of their atomic numbers and groups atoms with similar properties in the same vertical column (Figure 2.26).

samples that have the same mass ratio are

samples that have the same mass ratio are not necessarily the same substance. For example, there are many compounds other than isooctane that also have a carbon-to-hydrogen mass ratio of 5.33:1.00

spatial isomers

spatial isomers, in which there lative orientations of the atoms in space can be different

structural formula

structural formula for a compound gives the same information asitsmolecular formula(thetypesandnumbers of atoms in the molecule) but also shows how the atoms are connected in the molecule Fornow,simplyknowthatthelinesareanindication ofhowtheatomsare connectedinamolecule.

structural isomers

structural isomers, compounds in which the molecules differ in how the atoms are connected to each other

law of definite proportion

that all samples of a pure compound contain the same elements in the same proportion by mass.This statement is known as the law of definite proportion so the law of constant composition The suggestion that the numbers of atoms of the elements in a given compound always exist in the same ratio is consistent with these observations. For example, when different samples of isooctane (a component of gasoline and one of the standards used in the octane rating system) are analyzed, they are found to have a carbon-to-hydrogen mass ratio of 5.33:1

the atomic number also indicates the

the atomic number also indicates the number ofelectrons inanatom

group 1

the elements in group 1 (the first column) form compounds that consist of one atom of the element and one atom of hydrogen. These elements (except hydrogen) are known as alkali metals,andtheyallhavesimilarchemicalproperties

law of multiple proportions states

the law of multiple proportions states that when two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small, whole numbers

transitional metals form

transition metals and some other metals often exhibit variable charges that are not predictable by their location in the table. For example, copper can form ions with a 1+ or 2+ charge, and iron can form ions with a 2+ or 3+ charge.

rows 3-12 2 rows bottom table top row elements bottom row elements

transition metals in the columns labeled 3-12; and inner transition metals in the two rows at the bottom of the table (the top-row elements are called lanthanides and the bottom-row elements are actinides