Question

oxidation numbers
name ________ hour

element	metal or nonmetal	# of valence electrons	# of electrons gained or lost	oxidation number
k	metal	1	lose 1	k⁺
s	nonmetal	6	gain 2	s²⁻
se
ca
na
i
ga
cs
be
p
li
ne

Answer:

To solve for each element, we analyze their properties (metal/nonmetal, valence electrons, electron gain/loss, oxidation number) using periodic table trends:

1. Selenium (Se)

Step1: Classify (Nonmetal, Group 16)

Nonmetal (Group 16, like S).

Step2: Valence Electrons

Group 16 → 6 valence electrons.

Step3: Electrons Gained/Lost

Nonmetals gain electrons to reach 8 (octet). Needs \( 8 - 6 = 2 \) electrons → gain 2.

Step4: Oxidation Number

Gains 2 → charge \( -2 \) → \( \text{Se}^{2-} \).

2. Calcium (Ca)

Step1: Classify (Metal, Group 2)

Metal (Group 2, alkaline earth metal).

Step2: Valence Electrons

Group 2 → 2 valence electrons.

Step3: Electrons Gained/Lost

Metals lose electrons. Loses 2 to reach octet → lose 2.

Step4: Oxidation Number

Loses 2 → charge \( +2 \) → \( \text{Ca}^{2+} \).

3. Sodium (Na)

Step1: Classify (Metal, Group 1)

Metal (Group 1, alkali metal).

Step2: Valence Electrons

Group 1 → 1 valence electron.

Step3: Electrons Gained/Lost

Loses 1 to reach octet → lose 1.

Step4: Oxidation Number

Loses 1 → charge \( +1 \) → \( \text{Na}^+ \).

4. Iodine (I)

Step1: Classify (Nonmetal, Group 17)

Nonmetal (Group 17, halogen).

Step2: Valence Electrons

Group 17 → 7 valence electrons.

Step3: Electrons Gained/Lost

Gains \( 8 - 7 = 1 \) electron → gain 1.

Step4: Oxidation Number

Gains 1 → charge \( -1 \) → \( \text{I}^- \).

5. Gallium (Ga)

Step1: Classify (Metal, Group 13)

Metal (Group 13, post - transition metal).

Step2: Valence Electrons

Group 13 → 3 valence electrons.

Step3: Electrons Gained/Lost

Loses 3 to reach octet → lose 3.

Step4: Oxidation Number

Loses 3 → charge \( +3 \) → \( \text{Ga}^{3+} \).

6. Cesium (Cs)

Step1: Classify (Metal, Group 1)

Metal (Group 1, alkali metal).

Step2: Valence Electrons

Group 1 → 1 valence electron.

Step3: Electrons Gained/Lost

Loses 1 → lose 1.

Step4: Oxidation Number

Loses 1 → charge \( +1 \) → \( \text{Cs}^+ \).

7. Beryllium (Be)

Step1: Classify (Metal, Group 2)

Metal (Group 2, alkaline earth metal).

Step2: Valence Electrons

Group 2 → 2 valence electrons.

Step3: Electrons Gained/Lost

Loses 2 → lose 2.

Step4: Oxidation Number

Loses 2 → charge \( +2 \) → \( \text{Be}^{2+} \).

8. Phosphorus (P)

Step1: Classify (Nonmetal, Group 15)

Nonmetal (Group 15).

Step2: Valence Electrons

Group 15 → 5 valence electrons.

Step3: Electrons Gained/Lost

Gains \( 8 - 5 = 3 \) electrons → gain 3.

Step4: Oxidation Number

Gains 3 → charge \( -3 \) → \( \text{P}^{3-} \).

9. Lithium (Li)

Step1: Classify (Metal, Group 1)

Metal (Group 1, alkali metal).

Step2: Valence Electrons

Group 1 → 1 valence electron.

Step3: Electrons Gained/Lost

Loses 1 → lose 1.

Step4: Oxidation Number

Loses 1 → charge \( +1 \) → \( \text{Li}^+ \).

10. Neon (Ne)

Step1: Classify (Nonmetal, Noble Gas)

Nonmetal (Group 18, noble gas).

Step2: Valence Electrons

Group 18 → 8 valence electrons (stable octet).

Step3: Electrons Gained/Lost

Noble gases do not gain/lose electrons (already stable) → 0.

Step4: Oxidation Number

No charge (stable) → 0 (or \( \text{Ne} \), no ion).

Filled Table (Key Columns):

Element	Metal/Nonmetal	Valence Electrons	Electrons Gained/Lost	Oxidation Number
Ca	Metal	2	Lose 2	\( \text{Ca}^{2+} \)
Na	Metal	1	Lose 1	\( \text{Na}^+ \)
I	Nonmetal	7	Gain 1	\( \text{I}^- \)
Ga	Metal	3	Lose 3	\( \text{Ga}^{3+} \)
Cs	Metal	1	Lose 1	\( \text{Cs}^+ \)
Be	Metal	2	Lose 2	\( \text{Be}^{2+} \)
P	Nonmetal	5	Gain 3	\( \text{P}^{3-} \)
Li	Metal	1	Lose 1	\( \text{Li}^+ \)
Ne	Nonmetal	8	0 (no gain/loss)	0 (or \( \text{Ne} \))

(Note: For Ne, oxidation number is 0 as it is inert and does not form ions under normal conditions.)