Question

Which element has a total of three shells and has four electrons in its valence shell?

• A. $P$
• B. $O$
• C. $Si$
• D. $S$

Answer 1

The correct option is C

$\mathrm{Si}$

The outermost shell is the valence shell of the element. The elements in groups have similar electronic configuration of the valence shell.

The explanation for the correct option:

Number of valence electrons in the valence shell = 4

Number of valence electrons + 10= Number of group

So, the element belong to group 14.

Number of shells = 3

Number of shells = Number of period

So, the element belong to period 3.

Therefore, the element that has total of three shells and four electrons in valence shell is Silicon ($\mathrm{Si}$).

The explanation for the incorrect option:

Phosphorous ($\mathrm{P}$) consists of three shells but it has five electrons in valence shell.

Oxygen ($\mathrm{O}$) consists of two shells and six electrons in valence shell.

Sulphur ($\mathrm{S}$) consists of three shells but it has six electrons in valence shell.

Final answer:

Hence, option (C) is the correct option.