Question

Given below are the electronic configurations of some elements:

(a) 2,8,3

(b) 2,8,18,5

(c) 2,8,7

(d) 2,8,18,8,1

(e) 2,8,2

(f) 2,5

(g) 2,8,18,8

Answer the following:

(a) to which group does each belong?

Answer 1

The groups to which these elements belong are:

• The number of valence electrons in an element corresponds to the group which it belongs to.
• The number of shells corresponds to the period the element belongs to.
• The group and its valence electron:

1 = IA

2 = IIA

3 = IIIA

4 = IVA

5 = VA

6 = VIA

7 = VIIA

8 = 0

(a) 2,8,3 – The element has an atomic number (Z) 13. So, it is aluminum. It has 3 valence electrons so, it belongs to group IIIA.

(b) 2,8,18,5 - The element has an atomic number (Z) 33. So, it is arsenic. It has 5 valence electrons so, it belongs to group VA.

(c) 2,8,7 - The element has an atomic number (Z) 17. So, it is chlorine. It has 7 valence electrons so, it belongs to group VIIA.

(d) 2,8,18,8,1 - The element has an atomic number (Z) 37. So, it is rubidium. It has 1 valence electrons so, it belongs to group IA.

(e) 2,8,2 - The element has an atomic number (Z) 12. So, it is magnesium. It has 2 valence electrons so, it belongs to group IIA.

(f) 2,5 - The element has an atomic number (Z) 7. So, it is nitrogen. It has 5 valence electrons so, it belongs to group VA.

(g) 2,8,18,8 - The element has an atomic number (Z) 36. So, it is krypton. It has 8 valence electrons so, it belongs to group 0