Question

directions: complete the chart below.

element	number of valence electrons	# of electrons gained or lost to fill outer energy level	charge (oxidation number)
chlorine
beryllium
fluorine
lithium
oxygen
potassium
magnesium
phosphorous
aluminum

Explanation:

Step1: Find valence electrons

Valence electrons = group number (main groups):

• Sodium (Group1): $1$
• Chlorine (Group17): $7$
• Beryllium (Group2): $2$
• Fluorine (Group17): $7$
• Lithium (Group1): $1$
• Oxygen (Group16): $6$
• Potassium (Group1): $1$
• Magnesium (Group2): $2$
• Phosphorus (Group15): $5$
• Aluminum (Group13): $3$

Step2: Determine electron gain/loss

Atoms fill outer level (8 e⁻, except H/He):

• Metals lose electrons; nonmetals gain:
• Sodium: Lose $1$
• Chlorine: Gain $1$
• Beryllium: Lose $2$
• Fluorine: Gain $1$
• Lithium: Lose $1$
• Oxygen: Gain $2$
• Potassium: Lose $1$
• Magnesium: Lose $2$
• Phosphorus: Gain $3$
• Aluminum: Lose $3$

Step3: Calculate oxidation charge

Charge = -(e⁻ gained) or +(e⁻ lost):

• Sodium: $+1$
• Chlorine: $-1$
• Beryllium: $+2$
• Fluorine: $-1$
• Lithium: $+1$
• Oxygen: $-2$
• Potassium: $+1$
• Magnesium: $+2$
• Phosphorus: $-3$
• Aluminum: $+3$

Answer:

Element	Number of Valence Electrons	# of electrons gained or lost to fill outer energy level	Charge (Oxidation Number)
Chlorine	7	Gains 1	-1
Beryllium	2	Loses 2	+2
Fluorine	7	Gains 1	-1
Lithium	1	Loses 1	+1
Oxygen	6	Gains 2	-2
Potassium	1	Loses 1	+1
Magnesium	2	Loses 2	+2
Phosphorous	5	Gains 3	-3
Aluminum	3	Loses 3	+3