CHEMISTRY 161

1
CHEMISTRY 161 Chapter 2
2
Atomic Number and Mass Number
mass number (number of protons plus neutrons)
atomic number (number of protons) (number of
electrons)
3
Periodic Table of the Elements
period
g r o u p
4
atom (neutral)
take electron(s) (oxidation)
add electron(s) (reduction)
anion(Cl-) (negative charge)
cation(Na) (positive charge)
ion (charged)
5
3
2
1
0
-/4 -/2
-1
-2
-3
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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
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Homework Chapter 2, p. 43-61 problems,
group 1 8 elements