Chapter 4

Metals with Variable Charge

-Metals can have different charges in different compounds are usually (but not always) transition metals. -The charges of the transition metals cannot be inferred from their group number.

formula unit

-The basic unit of an ionic compound is the formula unit, the smallest, electrically neutral collection of ions. -not a molecule- it does not usually exist as a discrete entity but rather as part of a larger lattice.

crystalline lattice

-To understand that stability, we must account for the formation of a crystalline lattice as a result of the attractions between the cations and anions.

nomenclature

The process of naming compounds is called nomenclature.

naming rules

naming rules Cation Anion -If metal will form only ONE type of CATION= use name of metal -if metal will form only ONE type of ANION= ends with ide Example: CaCl2= Calcium chloride, Al2S3=Aluminum sulfide. S2-= Sulfide -If metal may from TWO or more type of CATIONS (usually transition metals)(d-block and f-block)= name of metal (Roman numeral)(charge) Example: Fe2O3= iron(iii) oxide, FeO= iron(ii) oxide

atomic mass

the average mass of an atom of an element as its atomic mass

bond strength

triple bond < double bond < single bond (shortest)-----------------------(longest)

mixture

-elements can mix in any proportion whatsoever -Hydrogen and Oxygen Mixture... This can have any ratio of hydrogen to oxygen.

molecular formula

-indicates the actual number of atoms of each element in a molecule of a compound. -The molecular formula is always a whole-number multiple of the empirical formula. -For some compounds, the empirical formula and the molecular formula are identical. For example, the empirical and molecular formula for water is H2O Molecular formula for COVALENT compounds only: -Actual # of atoms per molecule

ionic bonding and electron transfer

-ionic solid as a lattice of individual ions held together by coulombs forces that are not directional (means that as we move away from the center of an ion the forces are equally strong in all directions. -to melt the solid, significant amount of heat is required. high melting points for ionic solids -the movement or flow of electrons in response to an electric potential, or voltage, is electrical current -nonconductivity of ionic solids -when the ionic sold dissolves in water, the cation and anions dissociate, forming ions in solution. These ions move in response to electrical forces creating an electrical current. -ionic bonds are formed when a metal loses and electron and a nonmetal gains an electron

ball and stick molecular model

-represents atoms as balls and chemical bonds as sticks; how the two connect reflects a molecule's shape. -balls are typically color-coded to specific elements -carbon=black, hydrogen=white, nitrogen=blue, oxygen=red. Ball and stick molecular model in COVALENT compound only: -Ball=atom -Stick=bond

elements that exist as diatomic molecules

H2, N2, O2, F2, Cl2, Br2, I2 N2= very strong bond between the two nitrogen atoms. the bond is so strong that it is difficult to break, making N2 a relatively unreactivce molecule.

Nitrite

NO2 charge -1

Sulfate

SO4 charge -2

Mass Percent as a Conversion Factor

Since percent means per hundred, there are 58.64 grams Cl per hundred grams CCl2F2, which we express as the ratio: 58.64g Cl: 100g CCl2F2 -These ratios function as conversion factors between grams of Cl and grams of CCl2F2. For example, to calculate the mass of Cl in 1.00 kg CCl2F2

molar mass of a compound

an element's molar mass—the mass in grams of one mole of its atoms—is numerically equivalent to its atomic mass. -The molar mass of a compound—the mass in grams of 1 mol of its molecules or formula units—is numerically equivalent to its formula mass. -formula mass=molar mass (g/mol) -Avogadro's number to determine the number of atoms in a given mass of the element (formula units) (molecules)(6.022*10^23)

review

review -empirical formula= shows the smallest whole number ratio of atoms -molecular formula= shows actual number of each type of atom in the molecule -formula weight=molecular weight

ionic compound

-These oppositely charged ions attract one another according to Coulomb's law and form an ionic compound, which in the solid state is composed of a lattice—a regular three-dimensional array—of alternating cations and anions. -Example: The sodium, a metal, cation (loses electron) then attracts the chloride, a nonmetal, anion (gains electron), and the two form a crystalline lattice. -Ionic compounds do NOT form molecules, instead we refer to formula units (NaCl- For Sodium Chloride)

molecular compound

-Water is a covalent compound. These covalent compounds are molecular. -The shared electrons interact with the nuclei of both of the bonding atoms, lowering their potential energy in accordance with Coulomb's law. Covalently bonded atoms form molecules, and the resulting compounds are called molecular compounds.

naming binary ionic compounds

-naming binary ionic compound containing a metal that forms ONLY ONE TYPE of cation -Binary compounds contain only two different elements. The names of binary ionic compounds take the form: Name of cation (metal) and Base name of anion (nonmetal) + -ide anion name will end in -ide

Cyanide

CN- CN charge -1

carbonate

CO3 charge -2

Nitrate

NO3 charge -1

Phosphate

PO4 charge -3

double and triple covalent bonds

a double bond= would have 4 dots being shared by the two elements -In general, double bonds are shorter and stronger than single bonds. a triple bond= would have 6 dots being shred by the two elements -Triple bonds are even shorter and stronger than double bonds.

common polyatomic ions

acetate, carbonate, hydroxide, nitrate, nitrite, phosphate, sulfate, cyanide, Ammonium Most common polyatomic ions are OXYANIONS- anions containing oxygen and another element. -If there are only two ions in the series, the one with more oxygen atoms has the ending -ate and the one with fewer oxygen atoms has the ending -ite. Example: NO3- is nitrate and NO2- is nitrite -If there are more than two ions in the series, we use the prefixes hypo-, meaning less than, and per-, meaning more than. Example: ClO- is hypochlorite—less oxygen than chlorite and ClO4- is perchlorate—more oxygen than chlorate.

pervious principal shell

is the octet that the new element gains after it gives away its one electron.

naming ionic compounds containing polyatomic ions

naming ionic compounds containing polyatomic ions -Many common ionic compounds contain ions that are themselves composed of a group of covalently bonded atoms with an overall charge. -hypochlorite- disinfection

conversion factors from chemical formulas

-Chemical formulas contain within them inherent relationships between atoms (or moles of atoms) and molecules (or moles of molecules). -With ratios such as these—which come from the chemical formula—we can directly determine the amounts of the constituent elements present in a given amount of a compound without having to calculate mass percent composition. -1 mol CCl2F2 : 2 mol Cl -we can also find the mass of an element with using this conversion factor -the chemical formula gives us a relationship between the amounts (in moles) of substances, not between the masses (in grams) of them. when asked to find the mass of an element present in a given mass of a compound is... mass compound, moles compound, moles element, mass element.

combustion analysis

-Combustion is a type of chemical reaction. -In combustion analysis, the unknown compound undergoes combustion (or burning) in the presence of pure oxygen -When the sample is burned, all of the carbon in the sample is converted to CO2, and all of the hydrogen is converted to H2O -The CO2 and H2O are then weighed. With these masses we can use the numerical relationships b/n moles inherent in the formula for CO2 and H20 -We can determine the amounts of any other elemental constituents, such as O, Cl, or N, by subtracting the original mass of the sample from the sum of the masses of C and H -oxygen goes in the furnace with sample (unknown compound is burned in oxygen), then it goes to the H20 absorber, (water and carbon dioxide produced are isolated and weighed), finally it goes through the CO2 absorber, and lastly other substances not absorbed

naming binary ionic compounds

-Naming Binary Ionic Compounds Containing a Metal That forms MORE THAN ONE TYPE of cation -For these metals, the name of the cation is followed by a roman numeral (in parentheses), which indicates the charge of the metal in that particular compound. -The full names for compounds containing metals that form more than one kind of cation have the form: Name of cation (metal),(charge of cation (metal) in Roman numerals in parentheses), Base name of anion (nonmetal) +-ide The following are older name... -2+= -ous -3+= -ic -1+= -ous -4+= -ic

covalent bonding: models and reality

-The Lewis model predicts the properties of molecular compounds in many ways. We have already seen how it explains the existence of several diatomic elements. -The Lewis model also accounts for why covalent bonds are highly directional. -each bond links just one specific pair of atoms—in contrast to ionic bonds, which are nondirectional and hold together an entire array of ions. -in covalently bonded molecular compounds, the interactions between molecules (intermolecular forces) are generally much weaker than the bond- ing interactions within a molecule (intramolecular forces) -When a molecular compound melts or boils, the molecules themselves remain intact—only the relatively weak interactions between molecules must be overcome. Consequently, molecular compounds tend to have lower melting and boiling points than ionic compounds. -The covalent bonds between atoms of a molecule are much stronger than the interactions between molecules. To bring a molecular substance to a boil, only the relatively weak intermolecular forces have to be overcome,so molecular compounds often have low boiling points. -Strong covalent bonds within molecules -Weaker intermolecular forces between molecules

things to remember

-an ionic compound (metal and nonmetal) does not require prefixes -metals no prefixes -ionic compounds do not contain individual molecules -the smallest electrically neutral collection of ions is sometimes called a molecule but is more correctly called a formula unit.

space filling molecular model

-atoms fill the space between each other to more closely represent best estimates for how a molecule might appear if scaled to visible size. Space filling molecular model in COVALENT compounds only: -Shows approximately 90% of electron density.

structural formula

-communicates the most information -uses lines to represent covalent bonds and shows how atoms in a molecule are connected or bonded to each other. -Structural formulas can also indicate a sense of the molecule's geometry. -This version represents the approximate angles between bonds, giving a sense of the molecule's shape. -Structural formulas can also depict the different types of bonds that occur within molecules. -Two lines= double bond, which is generally stronger and shorter than a single bond, corresponds to two shared electron pairs -The structural formula for H2O2 is: H-O-O-H Structural formula for COVALENT compounds only: -Shows bonds (the connectivity) and shape

metals with invariant charges

-form cations with the same charges in all of their compounds. (Note that silver sometimes forms compounds with other charges, but these are rare.) -Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Al, Zn, Ag

formation of an ionic compound

-from its constituent elements usually gives off quite a bit of energy as heat (the process is exothermic) -The first ionization energy (+= indicated absorption of energy) (-= indicated the emission of energy)

chemical formula

-indicates the elements present in the compound and the relative number of atoms or ions of each. -For example, H2O is the chemical formula for water—it indicates that water consists of hydrogen and oxygen atoms in a two-to-one ratio. -Chemical formulas normally list the more metallic (or more positively charged) element first -followed by the less metallic (or more negatively charged) element Examples: NaCl (sodum chloride), CO2 (Carbon Dioxide), CCl4 (Carbon tetrachloride) Types of chemical formulas include: empirical formula, molecular formula, and structural formula. Chemical formulas for ionic compounds: # of each type of ion (covalent atom) Chemical formulas for covalent compounds only: consist of nonmetals

Empirical formula

-indicates the relative number of atoms of each element in a compound. -communicates the least. Empirical formula for IONIC compounds: -smallest whole number ratio. All ionic compounds are written as empirical formulas. Empirical formula for COVALENT compounds only: -May or may not be the same as the molecular formula

ionic bond

-metal and nonmetal (Table salt: NaCl) -the bond b/n a metal and nonmetal is an ionic bond. -metals tend to lose electrons/ then becomes a cation (positively charged ion) -nonmetals tend to gain electrons/ then becomes an anion (negatively charged ion) -electrostatic attractions b.n cations (+) and anions (-). These form a network of + and - ions packed together.

covalent bond

-nonmetal and nonmetal (H20) -The bond that forms between two or more nonmetals is a covalent bond -Bonds that form b/n neutral atoms (not charged), usually nonmetals -Nonmetals tend to have high ionization energies (their electrons are difficult to remove) so when they form bonds with another nonmetal, neither will transfer electrons to the other instead the two atoms SHARE some electrons. The stability of a covalent bond... -the most stable arrangement (the one with the lowest potential energy) of two positively charged particles separated by a small distance and a negatively charged particle. -shared electrons in a covalent chemical bond hold the bonding atoms together by attracting the positive charges of their nuclei.

formula mass

-the average mass of a molecule (or a formula unit) of a compound as its formula mass. -the term molecular mass and molecular weight are the same thing as formula mass -formula mass=formula weight=molecular weight= molar mass -the formula mass is the sum of the atomic masses of all the atoms in its chemical formula -formula mass (number of atoms of 1st element in chemical formula *atomic mass of 1st element)+(number of atoms of 2nd element in chemical formula *atomic mass of 2nd element)+ ... -amu is the unit for formula mass -molar mass is g/mol

lattice energy

-the energy associated with the formation of a crystalline lattice of alternating cations and anions from the gaseous ions. -The lattice energy of an ionic compound is the energy associated with the formation of a crystalline lattice of the compound from the gaseous ions. -When gaseous ions coalesce then heat is emitted. -network (3D arrangement in the crystal) -Coloumbs law F=k (q1q2)/d2 -q1=charge on cation -q2=charge on anion -d=distance b.n centers of cation and anion -in a lattice, strong attractions are there due to multiple cation-anion interactions -crystal lattice energy = E it takes to from crystal from gaseous ions (always negative) gaseous ions, give off energy. -Greater crystal lattice E means more negative -NOT just a matter of ionization energy and electron affinity!

ionic compound formulas

-the formula for the ionic compound composed of potassium and fluorine must be KF because, in compounds, K always forms 1+ cations and F always forms 1- anions. In order for the compound to be charge-neutral, it must contain one K+ cation to every one F- anion. -The formula for the ionic compound composed of magnesium and fluorine, in contrast, is MgF2 because Mg always forms 2+ cations and F always forms 1- anions. In order for this compound to be charge-neutral, it must contain one Mg2+ cation for every two F- anions. Summarizing ionic compound formulas... -Ionic compounds always contain positive and negative ions. -In a chemical formula, the sum of the charges of the positive ions (cations) must equal the sum of the charges of the negative ions (anions). -The formula of an ionic compound reflects the smallest whole-number ratio of ions.

chemical bond

A chemical bond is the force that holds atoms together in a compound. -forces that hold atoms together in compounds -Chemical bonds form because they lower the potential energy of the charged particles that compose atoms. -when an outer principal quantum level is completely full, the overall potential energy of the electrons that occupy that level is particularly low. Like those of noble gasses. The other elements do NOT posses stability so they form chemical bonds to become more stable a.k.a to lower potential energy -if these Interactions of attraction and repelling lead to an overall net reduction of potential energy b/n the charged particles, a chemical bond forms

Molecular models

A molecular model is a more accurate and complete way to specify a compound. -It includes a ball-and-stick molecular model, and a space-filling molecular model.

single covalent bonds

A shared pair of electrons is called a BONDING PAIR, while a pair that is associated with only one atom—and therefore not involved in bonding—is called a LONE PAIR. Lone pair electrons are also called nonbonding electrons. 2 dots= 1 line

acetate

C2H3O2- CH3COO- CH3CO2-

Determining a Chemical Formula from Experimental Data

Determining a Chemical Formula from Experimental Data So the first thing we must do is convert our data from mass (in grams) to amount (in moles). To get the smallest whole-number subscripts in our formula, we divide all the subscripts by the smallest one -If the subscripts are not whole numbers, multiply all the subscripts by a small whole number (see table) to determine whole-number subscripts. .20= multiply by 5, .40= multiply by 5, .80= multiply by 5 .25= multiply by 4, .75= multiply by 4 .33= multiply by 3, .66= multiply by 3 .50= multiply by 2

identifying an ionic compound

Formula begins w/ metal or ammonium (NH4+) everything else is the other (covalent) -list cation first, then anion empirical formula only... charges will "balance" *COMPOUNDS ARE NEUTRAL, NO CHARGE*

lewis dot for covalent compounds/ bonding

In the Lewis model, we represent covalent bonding with a Lewis structure, which depicts neighboring atoms as sharing some (or all) of their valence electrons in order to attain octets (or duets for hydrogen). -covalent compounds have covalent bonds which are shared electrons between nonmetals

Iorganic compounds

Inorganic compounds, on the other hand, originate from the Earth. Salt—mined from the ground or from the ocean—is a common example of an inorganic compound. -chemists could synthesize inorganic compounds in the laboratory

Ammonium

NH4 charge +1 NH4+ CATION

Hydroxide

OH- OH charge -1

naming ionic compounds

Some ionic compounds—such as NaCl (table salt) and NaHCO3 (baking soda)—have COMMON NAMES, which are nicknames of sorts learned by familiarity. -Chemists have also developed SYSTEMATIC NAMES for different types of compounds including ionic ones. -you can determine the systematic name from its chemical formula and you can deduce the formula of a compound from its systematic name -Remember, ionic compounds are usually composed of metals and nonmetals; any time we see a metal and one or more nonmetals together in a chemical formula, we assume that it is an ionic compound. We categorize ionic compound into two types depending on the metal in the compound: -1 metal forms only one the of ion -2 metal forms move than one type of ion, can form more than one type of cation (depending on the compound). specify its charge for a given compound. These metals are usually transition metals. However Zn and Ag, from cations with the same charge in all of their compounds, and some main-group metals, such as Pb and Sn, from more than one type of cation.

Carbon

The key element in organic chemistry, however, is carbon -In its compounds, carbon always forms four bonds. The simplest organic compound is methane or CH4. -The chemistry of carbon is unique and complex because carbon frequently bonds to itself to form chain, branched, and ring structures -Carbon can also form double bonds and triple bonds with itself and with other elements -This versatility allows carbon to serve as the backbone of millions of different chemical compounds

mass percent composition (mass percent)

The mass percent composition or mass percent of an element is that element's percentage of the compound's total mass. We calculate the mass percent of element X in a compound from the chemical formula as follows: mass parent of element X= ((mass of elect X in 1 mol of compound)/ (mass of 1 mol of the compound))*100 percent by mass= % of each element in compound x/100 *100 total should =100

Hydrocarbons

The simplest organic compounds are hydrocarbons, and they are composed of carbon and hydrogen. -Hydrocarbons compose common fuels such as oil, gasoline, liquid petroleum gas, and natural gas common hydrocarbons include... Methane CH4 Primary component of natural gas Propane C3H8 LP gas for grills and outdoor stoves n-butane C4H10 Common fuel for lighters n-Pentane C5H12 Component of gasoline Ethene C2H4 Ripening agent in fruit Ethyne C2H2 Fuel for welding torches the n stands for normal which means straight chain

compound

When two or more elements combine to form a compound, an entirely different substance results. -elements combine in fixed, definite proportions -Water (A Compound)... Water molecules have a fixed ratio of hydrogen (two atoms) to oxygen (one atom)

polyatomic ion

an ion composed of two or more atoms the charge on the hypochlorite ion is a property of the whole ion, not just the oxygen atom; this is true for all polyatomic ions. -We name ionic compounds that contain a polyatomic ion in the same way that we name other ionic compounds, except that we incorporate the name of the polyatomic ion whenever it occurs. -For example, NaNO2 is named according to its cation, Na+ , sodium, and its polyatomic anion, NO2-, nitrite. Its full name is sodium nitrite. -We name FeSO4 according to its cation, iron, its charge (II), and its polyatomic ion sulfate. Its full name is iron(II) sulfate. -If the compound contains both a polyatomic cation and a polyatomic anion, we use the names of both polyatomic ions. For example, NH4NO3 is ammonium nitrate.

calculating molecular formulas for compounds

calculating molecular formulas for compounds -We can determine the molecular formula of a compound from the empirical formula if we also know the molar mass of the compound. -the molecular formula is always a whole- number multiple of the empirical formula. -molecular formula = empirical formula * n, where n = 1, 2, 3,... -We also know that the molar mass is a whole-number multiple of the empirical formula molar mass, the sum of the masses of all the atoms in the empirical formula. -n = molar mass/ empirical formula molar mass the empirical formula molar mass is the regular mass of the whole compound -We can then use this value of n to find the molecular formula.

hydrates

hydrated ionic compounds -hydrates—contain a specific number of water molecules associated with each formula unit. -compound w/ water in crystal Example: Epsom sals is MgSO4*7H20, its systematic name is magnesium sulfate heptahydrate -Waters of hydration can usually be removed by heating the compound. -We name hydrates like we name other ionic compounds, but we give them the additional name "prefixhydrate," where the prefix indicates the number of water molecules associated with each formula unit. Hemi- 1/2 Mono- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5 Hexa- 6 Hepta- 7 Octa- 8 Nona- 9 Deca- 10 Undeca- 11 Dodeca- 12

Methane example

molecular, structural, ball and stick model, and space filling model. -The molecular formula of methane indicates the number and type of each atom in the molecule: one carbon atom and four hydrogen atoms. -The structural formula indicates how the atoms are connected: The carbon atom is bonded to the four hydrogen atoms. -The ball-and-stick model clearly portrays the geometry of the molecule: The carbon atom sits in the center of a tetrahedron (a three- dimensional geometrical shape characterized by four equivalent triangular faces.) formed by the four hydrogen atoms. -The space-filling model gives the best sense of the relative sizes of the atoms and how they merge together in bonding

Lewis model

named after the American chemist G. N. Lewis (1875-1946). -In the Lewis model, we represent valence electrons as dots and we draw Lewis electron-dot structures (or simply Lewis structures) to depict molecules. -have tremendous predictive power. -use the Lewis model to predict whether a particular set of atoms will form a stable molecule and what that molecule might look like. -Show valence elevons and pairing -for main-group elements, the valence electrons are those in the element's outermost principal energy level. -do not try to calculate the energies associated

lewis symbol

represent the valence electrons of main-group elements as dots surrounding the abbreviation for the element. -Each dot represents a valence electron -dots are placed around the element's symbol with a maximum of two dots per side. Remember... the number of valence electrons fr any main group is equal to the group number of the element (except for helium, which is in group 8A but has only two valence electrons, when down those two valence electrons are paired, duet, represent stable electron configuration for only helium ) -place dots singly before pairing -when atoms have eight valence electrons, they are stable, because they have a full outer principal level. There are an octet

molecular compounds

the formula for a molecular compound cannot always be determined from its constituent elements because the same combination of elements may form several different molecular compounds, each with a different formula -naming a molecular compound based on its formula and writing its formula based on its name -Remember, molecular compounds are composed of two or more nonmetals. Naming molecular compounds... -Prefix, Name of 1st element, prefix, Base name of 2nd element +-ide -write the name of the element with the smallest group number first. If they lie in the same group write the element with the greatest row number first. -Prefixes incude... mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 nona- 9 deca- 10 -If there is only one atom in the first element don't write mono -use mono only in the second element Examples: nitrogen triodide, phosphorus pentachloride, tetraphsophorus decasulfide

organic compounds

they designated organic compounds as those that origi- nate from living things. Sugar—from sugarcane or the sugar beet—is a common example of an organic compound. -chemists can NOT synthesize organic compounds in the laboratory. KEEP IN MIND THAT ORGANIC CHEM HAS CHANGED AND THEY CAN MAKE ORGANIC COMPOUNDS -Organic compounds are common in everyday substances. Many smells—such as those in perfumes, spices, and foods—come from organic compounds. -Organic compounds are the major components of living organisms. They are also the main components of most of our fuels, such as gasoline, oil, and natural gas, and they are the active ingredients in most pharmaceuticals, such as aspirin and ibuprofen. -The organic compound cinnamaldehyde is largely responsible for the taste and smell of cinnamon. -THEY ARE COMPOSED OF CARBON AND HYDROGEN and a few other elements including nitrogen, oxygen, and sulfur.