Chapter 2 Openstax Exercises
2.6 Molecular and Ionic Compounds 45. Using the periodic table, predict whether the following chlorides are ionic or covalent: KCl, NCl3, ICl, MgCl2, PCl5, and CCl4
.Ionic: KCl, MgCl2; Covalent: NCl3, ICl, PCl5, CCl4
ionic compounds are typically made (use periodic table)
In an ionic compound, the + and - charged atoms come together in an attractive bond. Thus typically this bond is made from one atom on the left side (nonmetals) of the PT while the other atom is from the right of the PT (metals)
57. Each of the following compounds contains a metal that can exhibit more than one ionic charge. Name these compounds: (a) Cr2O3 (b) FeCl2 (c) CrO3 (d) TiCl4 (e) CoO (f) MoS2
57.(a) chromium(III) oxide; (b) iron(II) chloride; (c) chromium(VI)(6) oxide; (d) titanium(IV) chloride; (e) cobalt(II) oxide; (f) molybdenum(IV) sulfid
59. The following ionic compounds are found in common household products. Write the formulas for each compound: (a) potassium phosphate (b) copper(II) sulfate (c) calcium chloride (d) titanium dioxide (e) ammonium nitrate (f) sodium bisulfate (the common name for sodium hydrogen sulfate)
59.(a) K3PO4; (b) CuSO4; (c) CaCl2; (d) TiO2; (e) NH4NO3; (f) NaHSO4
7. How are protons and neutrons similar? How are they different?
7.Both are subatomic particles that reside in an atom's nucleus. Both have approximately the same mass. Protons are positively charged, whereas neutrons are uncharged.
metals and non metals what do they form (anions or cations)
Generally, metals exist on the left side of the table and nonmetals on the right. The metals tend to lose electrons to form a + charge on an atom while the nonmetals tend to gain an electron to form a - charge on an atom.
11. Write the symbol for each of the following ions: (a) the ion with a 1+ charge, atomic number 55, and mass number 133 (b) the ion with 54 electrons, 53 protons, and 74 neutrons (c) the ion with atomic number 15, mass number 31, and a 3− charge (d) the ion with 24 electrons, 30 neutrons, and a 3+ charge
(a) 133Cs+; (b) 127 I −; (c) 31P3−; (d) 57Co3+ (given up 3 electrons, so need to add the charge to the electrons)
17. The following are properties of isotopes of two elements that are essential in our diet. Determine the number of protons, neutrons and electrons in each and name them. (a) atomic number 26, mass number 58, charge of 2+ (b) atomic number 53, mass number 127, charge of 1−
(a) atomic number 26, mass number 58, charge of 2+ (start (a) Iron, 26 protons, 24 electrons, and 32 neutrons (b) atomic number 53, mass number 127, charge of 1− p-53 e-54 n- 74 (b) iodine, 53 protons, 54 electrons, and 74 neutron
naming transitional metals
** The only difference here is that we have to specify the charge of the transition metal ion by using a Roman numeral The sum of the charges has top be zero Example: What is the correct name of CrCl3 ? The charge of Cr is unknown = x . But chloride = (-1). The sum of the charges has top be zero, so: x +3(-1) = 0. x = 3. Answer: CrCl3 = chromium (III) chloride.
29. Write the molecular and empirical formulas of the following compounds: 0=c=0 h-c=c-h (pg 129)
.(a) molecular CO2, empirical CO2; (b) molecular C2H2, empirical CH; (c) molecular C2H4, empirical CH2; (d) molecular H2SO4, empirical H2SO40=c=0
The procedure that can be followed when confronted with the name of a compound and you wish to write its formula is as follows
1. Identify the symbol of the cation (first part of the name) and the anion 2.Identify the valence or charge of each symbol and place it in parenthesis just above the symbol
naming covalent compounds
1. Understand a covalent compound. Covalent compounds are formed by two or more nonmetal elements. The name for the compound is based off how many atoms are present. The prefix attached is the Latin term for the number of molecules. 2.Learn the prefixes. Memorize the prefixes for up to 8 atoms: •1 atom - "Mono-" •2 atoms - "Di-" •3 atoms - "Tri-" •4 atoms - "Tetra-" •5 atoms - "Penta-" •6 atoms - "Hexa-" •7 atoms - "Hepta-" •8 atoms - "Octa-" Using the correct prefixes, name the new compound. You attach prefixes to any part of the compound that has multiple atoms.
naming ionic compounds
1. determine if compound is ionic. Ionic compounds contain a metal and a nonmetal. Refer to the periodic table. 2.For a two element ionic compound, the naming is simple. The first part of the name is the name of the metal element. The second part is the name of the nonmetal element, with the suffix "-ide." 3.Recognize transition metals. Metals in the D and F blocks of the periodic table are known as transition metals. Their charge is written with a Roman numeral when writing out the compound name. This is because they can have more than one charge and make more than one compound.
19. Give the number of protons, electrons, and neutrons in neutral atoms of each of the following isotopes: (a) 3 /7Li (b) 52/ 125Te (c) 47 /109Ag (d) 7/ 15N (e) 15/ 31P
19.(a) 3 protons, 3 electrons, 4 neutrons; (b) 52 protons, 52 electrons, 73 neutrons; (c) 47 protons, 47 electrons, 62 neutrons; (d) 7 protons, 7 electrons, 8 neutrons; (e) 15 protons, 15 electrons, 16 neutrons atomic number top (proton) mass number bottom (p+N)
43. Write a symbol for each of the following neutral isotopes. Include the atomic number and mass number for each. (a) the alkali metal with 11 protons and a mass number of 23 (b) the noble gas element with and 75 neutrons in its nucleus and 54 electrons in the neutral atom (c) the isotope with 33 protons and 40 neutrons in its nucleus (d) the alkaline earth metal with 88 electrons and 138 neutron
23/11 Na 129/54 Xe 73/33 As 226/88 Ra
25. The average atomic masses of some elements may vary, depending upon the sources of their ores. Naturally occurring boron consists of two isotopes with accurately known masses (10B, 10.0129 amu and 11B, 11.0931 amu). The actual atomic mass of boron can vary from 10.807 to 10.819, depending on whether the mineral source is from Turkey or the United States. Calculate the percent abundances leading to the two values of the average atomic masses of boron from these two countries.
25.Turkey source: 0.2649 (of 10.0129 amu isotope); US source: 0.2537 (of 10.0129 amu isotope (10.0129 x X) + (11.0931 x (1-X)) = 10.807 (10.0129X) + (11.0931-11.0931X) = 10.807 -11.0931 -11.0931X -1.0802x = -.2861 ---------------------- -1.0802 Turkey source: 0.2649
31. Determine the empirical formulas for the following compounds: (a) caffeine, C8H10N4O2 (b) fructose, C12H22O11 (c) hydrogen peroxide, H2O2 (d) glucose, C6H12O6 (e) ascorbic acid (vitamin C), C6H8O6
31.(a) C4H5N2O; (b) C12H22O11; (c) HO; (d) CH2O; (e) C3H4O3
33. Write the empirical formulas for the following compounds:
33.(a) CH2O; (b) C2H4O
but build a molecule with two carbons, six hydrogens, and one oxygen. (a) Draw the structural formula of this molecule and state its name. (b) Can you arrange these atoms to make a different molecule? If so, draw its structural formula and state its name. (c) How are the molecules drawn in (a) and (b) the same? How do they differ? What are they called (the type of relationship between these molecules, not their names).
35. (a) ethanol (b) methoxymethane, more commonly known as dimethyl ether (c) These molecules have the same chemical composition (types and number of atoms) but different chemical structures. They are structural isomers. (131) (1312)
37. Using the periodic table, classify each of the following elements as a metal or a nonmetal, and then further classify each as a main-group (representative) element, transition metal, or inner transition metal: (a) uranium (b) bromine (c) strontium (d) neon (e) gold (f) americium (g) rhodium (h) sulfur (i) carbon (j) potassium
37.(a) metal, inner transition metal; (b) nonmetal, representative element; (c) metal, representative element; (d) nonmetal, representative element; (e) metal, transition metal; (f) metal, inner transition metal; (g) metal, transition metal; (h) nonmetal, representative element; (i) nonmetal, representative element; (j) metal, representative element
39. Using the periodic table, identify the lightest member of each of the following groups: (a) noble gases (b) alkaline earth metals (c) alkali metals (d) chalcogens
39.(a) He; (b) Be; (c) Li; (d) O
41. Use the periodic table to give the name and symbol for each of the following elements: (a) the noble gas in the same period as germanium (b) the alkaline earth metal in the same period as selenium (c) the halogen in the same period as lithium (d) the chalcogen in the same period as cadmium
41.(a) krypton, Kr; (b) calcium, Ca; (c) fluorine, F; (d) tellurium, T
47. For each of the following compounds, state whether it is ionic or covalent. If it is ionic, write the symbols for the ions involved: (a) NF3 (b) BaO, (c) (NH4)2CO3 (d) Sr(H2PO4)2 (e) IBr (f) Na2O
47.(a) covalent; (b) ionic, Ba2+, O2−; (c) ionic, NH4+ , CO32−; (d) ionic, Sr2+, H2PO4−; (e) covalent; (f) ionic, Na+, O2−
49. For each of the following pairs of ions, write the symbol for the formula of the compound they will form: (a) Ca2+, S2− (b) NH4+ , SO42− (c) Al3+, Br− (d) Na+, HPO42− (e) Mg2+, PO43-
49.(a) CaS; (b) (NH4)2SO3; (c) AlBr3; (d) Na2HPO4; (e) Mg3 (PO4)2
2.7 Chemical Nomenclature 51. Name the following compounds: (a) CsCl (b) BaO (c) K2S (d) BeCl2 (e) HBr (f) AlF3
51.(a) cesium chloride; (b) barium oxide; (c) potassium sulfide; (d) beryllium chloride; (e) hydrogen bromide; (f) aluminum fluoride
53. Write the formulas of the following compounds: (a) rubidium bromide (b) magnesium selenide (c) sodium oxide (d) calcium chloride (e) hydrogen fluoride (f) gallium phosphide (g) aluminum bromide (h) ammonium sulfate
53.(a) RbBr; (b) MgSe; (c) Na2O; (d) CaCl2; (e) HF; (f) GaP; (g) AlBr3; (h) (NH4)2SO4
55. Write the formulas of the following compounds: (a) chlorine dioxide (b) dinitrogen tetraoxide (c) potassium phosphide (d) silver(I) sulfide (e) aluminum nitride (f) silicon dioxide
55.(a) ClO2; (b) N2O4; (c) K3P; (d) Ag2S; (e) AlN; (f) SiO2
23. Average atomic masses listed by IUPAC are based on a study of experimental results. Bromine has two isotopes 79Br and 81Br, whose masses (78.9183 and 80.9163 amu) and abundances (50.69% and 49.31%) were determined in earlier experiments. Calculate the average atomic mass of bromine based on these experiments.
79.904 amu
how to find the average atomic mass
Atomic mass is a calculation of the mass of an element, when taking into account the varying mass number of its isotopes. Although each isotope shares the same number of protons and electrons, they have varying numbers of neutrons. You must also factor in the overall abundance of the isotope and solve for a weighted average 1. You will need to gather the abundance and mass for each of the isotopes. 2. List your isotopes on your paper in chart form. Place a column for abundance and a column for atomic mass. •For example, there are 2 naturally occurring isotopes of silver, 107Ag and 109Ag. The atomic mass of 107Ag is 106.90509 atomic mass unit (amu) and the abundance is 51.86. The atomic mass of 109Ag is 108.90470 amu and the abundance is 48.14. •If you know all but 1 of the abundance percentages, you can subtract from 100 to calculate the abundance of the remaining isotope. The abundance figures must add up to 100.
Anions (Negative Ions) Group 17 are 1- (will end with -ide) Group 16 are 2- (will end with -ide) Group 15 are 3- (will end with -ide) Polyatomic Ions -just use its charge. (Generally ends with -ate or -ite, watch out for hydroxide OH- and cyanide CN-)
Cations (Positive Ions) All Group 1 elements in the Periodic Table are +1 in compounds. All Group 2 elements in the Periodic Table are +2 in compounds. Transition elements (have a few charges) will have a Roman Numeral to tell you what positive charge to use. silver is 1+, Zinc is 2+ and Aluminum is 3+ Polyatomic Ions -just use its charge.
5. The existence of isotopes violates one of the original ideas of Dalton's atomic theory. Which one
Dalton originally thought that all atoms of a particular element had identical properties, including mass. Thus, the concept of isotopes, in which an element has different masses, was a violation of the original idea. To account for the existence of isotopes, the second postulate of his atomic theory was modified to state that atoms of the same element must have identical chemical properties
***Dalton's Atomic Theory****
Dalton's Atomic Theory 1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms. Modern atomic theory is, of course, a little more involved than Dalton's theory but the essence of Dalton's theory remains valid. Today we know that atoms can be destroyed via nuclear reactions but not by chemical reactions. Also, there are different kinds of atoms (differing by their masses) within an element that are known as "isotopes", but isotopes of an element have the same chemical properties.
15. Open the Build an Atom simulation (http://openstaxcollege.org/l/16PhetAtomBld) (a) Drag protons, neutrons, and electrons onto the atom template to make a neutral atom of Lithium-6 and give the isotope symbol for this atom. (b) Now remove one electron to make an ion and give the symbol for the ion you have created.
Lithium-6 contains three protons, three neutrons, and three electrons. The isotope symbol is 6Li or 3 6Li. (b) 6Li+ or 3 6Li+
percent abundance
Percent abundance can be calculated by finding the percentage of an isotope compared to another isotope of an element using its relative atomic mass. This is an algebraic process and depends upon several measurements. hint: its atomic weight is a calculation of the atomic masses and relative abundances of each isotope of that element.
roman numerals
Roman numeral I +1 II +2 III +3 IV +4 V +5 VI +6
what is a natural atom
The atom of each element is made up of electrons, protons and neutrons. All atoms of the same neutral element have the same number of protons and electrons but the number of neutrons can differ. Atoms of the same element but different neutrons are called isotopes.
covalent compounds (use periodic table)
The covalently bonded compounds, on the other hand, typically come from two nonmetals on the right hand side of the table. Since nonmetals tend to form - charged atoms, the attraction between two - charged atoms is obviously not a +/- charge. It is nothing like this because the outer electrons of both atoms rearrange themselves to form a more stable arrangement of shared electrons between the two atoms
The starting materials consist of one green sphere and two purple spheres. The products consist of two green spheres and two purple spheres does this follow daltons law?
The products consist of two green spheres and two purple spheres. This violates Dalton's postulate that that atoms are not created during a chemical change, but are merely redistributed
27. Explain why the symbol for an atom of the element oxygen and the formula for a molecule of oxygen differ
The symbol for the element oxygen, O, represents both the element and one atom of oxygen. A molecule of oxygen, O2, contains two oxygen atoms; the subscript 2 in the formula must be used to distinguish the diatomic molecule from two single oxygen atoms
Naming Polyatomic Compounds (polyatmoic: consisting of many atoms.)
These compounds are built off of groups of atoms that are bonded together, and the entire group has a positive or negative charge. You can do three basic things to polyatomic compounds: Polyatomic ions are ions which consist of more than one atom. For example, nitrate ion, NO3-, contains one nitrogen atom and three oxygen atoms. The atoms in a polyatomic ion are usually covalently bonded to one another, and therefore stay together as a single, charged unit. 1. name cation first and anion second 2.When the formula unit contains two or more of the same polyatomic ion, that ion is written in parentheses with the subscript written outside the parentheses. 3.
Identify the postulate of Dalton's theory that is violated by the following observations: 59.95% of one sample of titanium dioxide is titanium; 60.10% of a different sample of titanium dioxide is titanium.
This statement violates Dalton's fourth postulate: In a given compound, the numbers of atoms of each type (and thus also the percentage) always have the same ratio.
molecular compound empirical formulas
a formula giving the number of atoms of each of the elements present in one molecule of a specific compound. empirical formula of a chemical compound is the simplest positive integer ratio of atoms present in a compound
mass number atomic number
mass number- total numbers of protons/neutrons atomic number -is the number of protons found in the nucleus of an atom of that element,
13. Open theBuild an Atom simulation (http://openstaxcollege.org/l/16PhetAtomBld) and click on the Atom icon. (a) Pick any one of the first 10 elements that you would like to build and state its symbol. (b) Drag protons, neutrons, and electrons onto the atom template to make an atom of your element. State the numbers of protons, neutrons, and electrons in your atom, as well as the net charge and mass number. (c) Click on "Net Charge" and "Mass Number," check your answers to (b), and correct, if needed. (d) Predict whether your atom will be stable or unstable. State your reasoning. (e) Check the "Stable/Unstable" box. Was your answer to (d) correct? If not, first predict what you can do to make a stable atom of your element, and then do it and see if it works. Explain your reasoning.
net charge= has a charge if doesn't have equal numbers of protons and electrons mass number= total of protons and neutrons (brellium: 4 protons and 4 neutrons) stable or unastable= In summary it is the balance of protons and neutrons in a nucleus which determines whether a nucleus will be stable or unstable. Too many neutrons or protons upset this balance disrupting the binding energy from the strong nuclear forces making the nucleus unstable.