Question

The effective nuclear charge of an element with three valence electrons is $\mathrm{2.60.}$ What is the atomic number of the element?

• A. 1
• B. 2
• C. 3
• D. 4
• E. 5

Answer 1

Answer: (E)

$\because$ Effective nuclear charge $=2.60$

and valency shell contain 3 electrons.

Thus, minimum number of main shells for the given element are two i.e $(n=2)$ and its configuration will be $1s^2,2s^{2}2p^1$.

Thus, the given element has 5 electrons in all. Also, for a neutral atom.

$\because$ No. of electrons $=$ Atomic number

Thus, atomic number of the element is $5.$