Question

On the basis of the electronic configuration of ${}_5\mathrm{X}^9$, the group number and period of the element ‘$\mathrm{X}$’ is :

• A. Group 15 period 2
• B. Group 13 period 2
• C. Group 9 period 5
• D. Group 13 period 5

Answer 1

The correct option is B

Group 13 period 2

Explanation for correct answers:

Option B Group 13 period 2

• The periodic table is a tabular display of the chemical elements.
• The elements in the periodic table are arranged in order of atomic number.
• The periodic table consists of 18 groups and 5 periods.
• A period is the elements that are arranged in a horizontal row of the periodic table.
• A group is the elements that are arranged in a vertical row of the periodic table.
• The element can be uniquely represented as ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}$, where $\mathrm{X}$ is the atomic symbol of the element, $\mathrm{A}$ is the mass number and $\mathrm{Z}$ is the atomic number.
• Since the electronic configuration is given as ${}_5{}^9\mathrm{X}$, the group number of the given element ‘$\mathrm{X}$’ 9 is the mass number and 5 is the atomic number.
• Hence the element with the atomic number 5 is Boron$\left(\mathrm{B}\right)$, and in the periodic table, Boron is in group 13

Explanation for incorrect answers:

Option A Group 15 period 5

• The element with the atomic number 5 is Boron$\left(\mathrm{B}\right)$, and in the periodic table, Boron is in group 13
• Hence Option B is incorrect.

Option C Group 9 period 5

• The element with the atomic number 5 is Boron$\left(\mathrm{B}\right)$, and in the periodic table, Boron is in group 13
• Hence Option C is incorrect.

Option D Group 13 period 5

• The element with the atomic number 5 is Boron$\left(\mathrm{B}\right)$, and in the periodic table, Boron is in group 13
• Hence Option D is incorrect.