1. CHEMISTRY 161
Chapter 2

2. Atomic Number and Mass Number
(number of protons plus neutrons)
atomic number
(number of protons)
(number of electrons)

3. Periodic Table of the Elementsg r o u p

4. atom anion(Cl-) cation(Na+) ion (neutral) add electron(s)
(reduction)
take electron(s)
(oxidation)
anion(Cl-)
(negative charge)
cation(Na+)
(positive charge)
ion
(charged)

5. -1 -2 -3
-/+4
-/+2 +3 +2 +1 +0

6. Reaction of potassium (K) with sulfur (S)
/ × 2
(1) K → K+ + e-
(2) S + 2 e- → S-2
/ × 1
(1) 2 K → 2 K+ + 2 e-
(2) S + 2 e- → S-2
(1)+(2) 2K + S + 2e-→ K2S +2e-
(1)+(2) 2 K + S→ K2S

7. problems, group 1 – 8 elements
Homework
Chapter 2, p
problems, group 1 – 8 elements