Chemistry 100
Clark College
CHEM 100 Exam 2 Review – Updated for Fall 2007
You should feel comfortable with the following topics:
Ch. 4:
• Dalton’s postulates, and how they break down.
• Organization of an atom (p, n in nucleus, e- around the outside).
• Properties of atoms, subatomic particles.
• Regions of the periodic table, terminology.
• Atomic symbols – Z, A, counting p, n, e-.
• Isotopes and determining the average atomic mass.
• Forming ions and predicting the charge from the periodic table.
Ch. 9:
• The organization of the electrons and the Bohr model.
• Pictures/shapes of orbitals (s, p and d only)
• Rules for filling in electrons: Pauli Exclusion Principle, the Aufbau Principle, and Hund’s Rule.
• Filling in orbital diagrams (boxes and arrows).
• Writing electron configurations off of the periodic table (with and without the noble gas shortcut).
• Determining the number of valence electrons.
• Electron configurations for ions.
Ch. 5:
• Classifying pure substances as various types of elements or compounds.
• The diatomic elements.
• Writing balanced formula for ionic compounds.
• Naming ionic compounds, acids, and binary molecular compounds.
• Know your ion list! Charges and names!!
• Formula weights.
Review Problems – for a more complete review, redo homework, the nomenclature practice sheet and
in-class problems as well!
1. A new fictitious element is discovered on campus, and has been named Clarkium (Ck). Several
isotopes have been found, and their relative abundances have been determined:
Isotope
Mass
% Abundance
Ck – 307
306.982 amu
31.68
Ck – 309
309.053 amu
48.65
Ck – 310
309.997 amu
19.67
Using this data, find the average atomic weight of Clarkium (Ck).
2. A fictitious element, Nadinium, has the following isotopes, with their relative abundances:
Isotope
Mass
% Abundance
Nd – 197
196.98427 amu
37.86
Nd – 199
199.00352 amu
48.31
Nd – 200
200.01003 amu
13.83
Determine the average atomic weight of Nadinium.
Exam 2 Review
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Chemistry 100
Clark College
3. Write the full atomic symbols for titanium-48, arsenic-73, and barium-139.
4. Write out the electronic configuration for Cobalt (Z = 27). Cobalt typically makes two different,
stable cations. By analyzing the electronic configuration, predict the two stable cations of cobalt.
Explain your choices.
5. Fill in the following table on electronic configurations. Provide the ground-state electronic
configuration (you may use the noble-gas short hand), the number of valence electrons, and use an
orbital diagram to determine the number of unpaired valence electrons.
Valence
electrons?
Configuration
Unpaired
electrons?
a) Si
b) Ag
c) Se-1
d) Cr3+
6. How many unpaired electrons does Te (Z = 52) have?
7. Give the electronic configuration for the following elements and ions. You may use the short cut.
Element
Configuration
Si
Ca
Ag
Ge2+
8. Nomenclature.
a) Give the formula for the neutral (balanced) compound described.
1. Sodium sulfate
2. Copper (II) perchlorate
3. Tin (IV) fluoride
4. Nitric acid
b) Give the name of the compound from the formula given.
1. H2CO3
2. KC2H3O2
3. N3Br5
4. CaS
Exam 2 Review
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Chemistry 100
Clark College
9. The neutral atoms of all the isotopes of the same element have
a) the same number of neutrons.
c) the same mass numbers.
b) the same number of electrons.
d) different numbers of protons.
10. How many neutrons are there in the chloride ion,
a) 17
b) 18
35
17
Cl-1 ?
c) 19
d) 21
11. How many protons, neutrons and electrons are in the antimony (III) ion,
123
51
e) 28
Sb+3 ?
a) 123 p, 72 n, 123 e-
d) 51 p, 72 n, 54 e-
b) 51 p, 72 n, 48 e–
e) 48 p, 72 n, 51 e -
c) 51 p, 72 n, 51 e12. The atomic mass of Ga is 69.72 amu. There are only two naturally occurring isotopes of gallium,
69
Ga with a mass of 69.0 amu and 71Ga with a mass of 71.0 amu. The natural abundance of the
71
Ga isotope is approximately
a) 20%
b) 40%
c) 50%
d) 60%
e) 80%
13. The formulas of the carbonate ion, the ammonium ion and the perchlorate ion are:
a) CO3-2, NH2+, ClO4-
c) CO2-2, NH4+, ClO3-
b) CO3-2, NH3+, ClO4+
d) CO3-2, NH4+, ClO4-
14. The group(s) that readily form cations is(are) the:
1. Alkali elements.
2. Halogen elements.
3. Transition metals.
a) 1 only
d) 1 and 2 only
b) 2 only
e) 1 and 3 only
c) 3 only
15. What is the molar mass (formula weight) of ammonium sulfate, (NH4)2SO4, an important synthetic
fertilizer?
a) 7.0 x 101 amu
d) 132 amu
b) 92 amu
e) 146 amu
c) 114 amu
16. What is the molar mass of Aspartame, C14H18N2O5, the active ingredient of NutraSweet, sold as
Equal ®?
a) 43.025 amu
c) 294.3 amu
b) 147.140 amu
d) 294.280 amu
Exam 2 Review
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