Question

directions: fill in the chart with the number of electrons on the outer shell.
element # valence electrons
be
na
al
c
cl
ar
he
o
rb
s
the periodic table of elements

Explanation:

Step1: Recall the rule for valence electrons

For main - group elements (groups 1 - 2 and 13 - 18), the number of valence electrons is equal to the group number. For group 1: \(n = 1\), group 2: \(n = 2\), group 13: \(n=3\), group 14: \(n = 4\), group 15: \(n=5\), group 16: \(n = 6\), group 17: \(n=7\), group 18: \(n = 8\) (except He which has 2).

Step2: Determine the group of each element

• Be: Group 2. So, the number of valence electrons \(n = 2\).
• Na: Group 1. So, the number of valence electrons \(n = 1\).
• Al: Group 13. So, the number of valence electrons \(n = 3\).
• C: Group 14. So, the number of valence electrons \(n = 4\).
• Cl: Group 17. So, the number of valence electrons \(n = 7\).
• Ar: Group 18. So, the number of valence electrons \(n = 8\).
• He: Group 18. But He has only 1 electron shell, and its valence - electron number \(n = 2\).
• O: Group 16. So, the number of valence electrons \(n = 6\).
• Rb: Group 1. So, the number of valence electrons \(n = 1\).
• S: Group 16. So, the number of valence electrons \(n = 6\).

Answer:

Element	# Valence Electrons
Na	1
Al	3
C	4
Cl	7
Ar	8
He	2
O	6
Rb	1
S	6