Chapter 2 – Atoms, Molecules, and Ions
____________Dr. Pahlavan
1. Determine the number of protons, electrons, and neutrons in the followings:
a)
65
Zn
b) cobalt-60
c) sodium
d)
52
Cr3+
e)
130
I-
2. For each of the following elements, write its chemical symbol or name, and indicate the
type and group to which it belongs:
a) potassium
b) arsenic
c) iodine
d) iron
e) Ca
3. Determine the empirical formulas for the following compounds:
a) C6H10O2
b) Si3O9
c) N2O4
e) CH4
4. Predict the charges of the ions of the followings:
a) Al
b) OH
c) O
d) SO4
e) HSO3
f) S4N4
f) ClO
5. Predict the empirical formula for the ionic compounds formed by followings:
a) Ca2+ , PO43b) K+ , NO3−
c) Al3+ , OH−
d) Ba2+ , HCO3−
6. Predict whether each of the following compound is molecular or ionic:
a) NaClO
b) NOCl
c) CoCO3
d) SCl2
7. Give names or chemical formulas for the following acids:
a) H2S
b) Nitric acid
c) perbromic acid
e) H2SO3
f) HClO2
g) Acetic acid
d) HI
h) HCN
8. Provide names or chemical formulas for the followings:
a) Cr(NO3)3
b) silver nitrate
c) Cr2O3
e) Lead(IV) acetate
f) dinitrogen trioxide
g) S4N4
d) Fe(NO2)2
h) KClO
9. Give a chemical formula or name for the followings:
a) chlorate ion
b) oxide ion
c) barium ion
e) AlN
d) hydrogencarbonate ion
e) HSO3f) S2g) Fe3+
h) H3O+
10. Naturally occurring magnesium has the following isotopic abundances:
Isotope Abundance
Mass
Mg-24
78.70%
23.98504
Mg-25
10.13%
24.98584
Mg-26
11.17%
25.98259
Calculate the average atomic mass of magnesium.
11. What is the difference between hydroacid and oxyacid? Give two examples of each.
Chapter 2 – Atoms, Molecules, and Ions (answers)
Dr. Pahlavan
1. Determine the number of protons, electrons, and neutrons in the followings:
a) 65 Zn
c) sodium
e) 130 I-
 30p, 35n, 30e 11p, 12n, 11e 53p, 77n, 54e-
b) cobalt-60  27p, 33n, 27ed) 52 Cr3+
 24p, 28n, 21e-
2. For each of the following elements, write its chemical symbol or name, and indicate the
type and group to which it belongs:
a) potassium (K, metal, group 1)
c) iodine (I, nonmetal, group 7)
e) Ca ( Calcium, metal, group 2)
b) arsenic (As, semimetal, group 5)
d) iron ( Fe, metal, transition metal)
3. Determine the empirical formulas for the following compounds:
a) C6H10O2 (C3H5O)
e) CH4
(CH4 )
b) Si3O9 (SiO3)
f) S4N4 (SN)
c) N2O4 (NO2)
4. Predict the charges of the ions of the followings:
a) Al (+3)
b) OH (-1)
c) O (-2)
d) SO4(-2)
e) HSO3 (-1)
f) ClO (-1)
5. Predict the empirical formula for the ionic compounds formed by followings:
a) Ca2+ , PO43−
Ca3(PO4)2
3+
−
c) Al , OH Al(OH)3
b) K+ , NO3d) Ba2+ , HCO3-
KNO3
Ba(HCO3)2
6. Predict whether each of the following compound is molecular or ionic:
a) NaClO (I)
b) NOCl (M)
c) CoCO3 (I)
d) SCl2 (M)
7. Give names or chemical formulas for the following acids:
a) H2S hydrosulfuric acid
c) perbromic acid HBrO4
e) H2SO3
Sulfurous acid
g) Acetic acid HC2H3O2
b) Nitric acid HNO3
d) HI hydroiodic acid
f) HClO2
h) HCN
Chlorous acid
hydrocyanic acid
e) AlN (I)
8. Provide names or chemical formulas for the followings:
a) Cr(NO3)3 Chromium(III)nitrate
c) Cr2O3 Chromium(III) oxide
e) Lead(IV) acetate Pb(C2H3O2)4
g) S4N4 tetrasulfur tetra nitride
b) silver nitrate
AgNO3
d) Fe(NO2)2 Ferrous nitrite
f) dinitrogen trioxide
N 2O 3
h) KClO potassium hypochlorite
9. Give a chemical formula or name for the followings:
a) chlorate ion ClO3c) barium ion Ba+2
e) HSO3bisulfite ion
3+
g) Fe
Ferric ion
b) oxide ion O-2
d) hydrogencarbonate ion HCO3f) S2- sulfide ion
h) H3O+ hydronium ion
10. Naturally occurring magnesium has the following isotopic abundances:
Isotope
Abundance
Mass
Mg-24
78.70%
23.98504
Mg-25
10.13%
24.98584
Mg-26
11.17%
25.98259
Calculate the average atomic mass of magnesium.
(0.787)(23.98504) + (0.1013)(24.98584) + (0.1117)(25.98259) = 24.31 amu
11. What is the difference between hydroacid and oxyacid? Give two examples of each.
Hydroacids do not have oxygen in the their formula (HCl, HBr, H2S)
Oxyacids contain oxygen in their formula (HNO3, H2SO4, H3PO4)