Question

The effective nuclear charge of an element with three valence electrons is 2.60. What is the minimum atomic number of the element?

• A. 5
• B. 4
• C. 3
• D. 2

Answer 1

Answer: (A)

As effective nuclear charge is 2.60 and valence shell contain 3 electrons so the minimum number of main shells for the given element are two i.e., (n = 2) and its configuration will be $1s^2,2s^2,2p^1$ .
Hence the given element has 5 electrons in all.
Also, for a neutral atom.
As number of electrons = atomic number = 5.
Thus, the atomic number of the element is 5.