Question

How many valence electrons does an atom of gallium possess?
A. 1
B. 3
C. 5
D. 7

Answer 1

In 1913, British physicist Henry Mosley arranged elements in the periodic table based on their atomic number. Currently, the periodic table has a total of 118 elements. It has 18 groups and 7 periods. The elements in the periodic table can be divided into four types based on their outermost electronic configuration and their properties. They are, s-, p-, d- and f- block elements.

Complete answer:
Group 1 and 2 comes under s-block elements since they have valence electrons in the s-subshell. Group 3 to group 12 comes under d- and f- block elements since they have valence electrons in d- and f- subshell. Group 3 to group 18 comes under p-block elements since they have valence electrons in the p-subshell.
Gallium has atomic number 31 and the symbol “Ga”. It belongs to group-13. Group-13 elements are Boron, Aluminium, Gallium, Indium, and Thallium. In the periodic table, the elements in the groups have the general electronic configuration, and periods have the elements whose electronic configuration differs by one unit. The elements in group-13 have the general electronic configuration and it can be written as $n{s^2}n{p^1}$. Where, n-principal quantum number.
The valence electronic configuration of gallium can be written as $4{s^2}4{p^1}$.

Hence, option B is the correct option..

Note: Pure gallium is a soft and silvery metal. It mainly presents under the earth’s crust. It is mainly used in electronic circuits and semiconductors. It is also used in the medical field such as high-temperature thermometers and barometers etc. Solid gallium is bluish-grey metal and china produces more than $95\%$ raw solid bluish-grey gallium.