Question

Which element has:

(a) two shells, both of which are completely filled with electrons?
(b) the electronic configuration 2, 8, 2?
(c) a total of three shells, with four electrons in its valence shell?
(d) a total of two shells, with three electrons in its valence shell?
(e) twice as many electrons in its second shell as its first shell?

Answer 1

(a) Neon with atomic number 10.
Electronic configuration:- Shells: K L
Electrons arranged: 2 8

(b) Magnesium is the element with the electronic configuration of 2,8,2 as its atomic number is 12, since the atomic number is the sum of all the electrons present in the electronic configuration.
Electronic configuration:- Shells: K L M
Electrons arranged: 2 8 2

(c) Silicon is an element with a total of three shells and four electrons in its valence shell. Its atomic number is 14 and the electronic configuration is 2,8,4.
Electronic configuration:- Shells: K L M
Electrons arranged: 2 8 4

(d) Boron is an element with a total of two shells, with three electrons in its valence shell. Its atomic number is 5 and electronic configuration is 2,3.
Electronic configuration:- Shells: K L
Electrons arranged: 2 3

(e) Carbon is the element with twice as many electrons in its second shell as its first shell. The atomic number of carbon is 6 and its electronic configuration is 2,4.
Electronic configuration:- Shells: K L
Electrons arranged: 2 4