Question

General electronic configuration of outermost and penultimate shell is $[Ne](n - 1){s^2}(n - 1){p^6}(n - 1){d^5}n{s^2}.$If $n = 4,$ then the number of protons in the nucleus will be.
A. $ > 25$
B. $ > 24$
C. $25$
D. $30$

Answer 1

Hint:Electronic configuration is the distribution of electrons of an atom or molecule into different shells, subshells of orbitals in an atom. The electrons are filled in increasing order of energy of the shells/subshells/orbitals. Outermost shell contains the valence electrons while the penultimate shell is the shell just before the valence shell.

Complete step-by-step answer:The general electronic configuration of outermost and penultimate shell is $[Ne](n - 1){s^2}(n - 1){p^6}(n - 1){d^5}n{s^2}.$If $n = 4,$the electronic configuration is $[Ne]3{s^2}3{p^6}3{d^5}4{s^2}$.
We all know that Total number of electrons in Neon is $10$.
The electronic configuration of Ne is $1{s^2}2{s^2}2{p^6}$
The total electronic configuration of the given element becomes $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^5}4{s^2}$
We know that
Atomic number $ = $number of protons/electrons for a neutral atom
Total number of electrons in Neon is $10$.
Number of electrons $ = $$10 + 2\left( {3s} \right) + 6\left( {3p} \right) + 5\left( {3d} \right) + 2\left( {4s} \right)$
Atomic number $ = $$25$
Now, number of protons $ = $atomic number
$\therefore $Number of protons $ = $$25$

Additional Information:The application of electronic configuration is in the rationalization of chemical properties, in both inorganic and organic chemistry. The electronic configurations, along with some simplified form of molecular orbital theory, have become the modern equivalent of valence concepts describing the number and type of chemical bonds that an atom can be expected to form.

Hence, the correct option is (C).

Note:Electronic configuration describes each electron as moving independently in an orbital, in an average field created by all other orbitals. The electronic configuration of different atoms is useful in understanding the structure of the periodic table of elements. This is also useful for describing the chemical bonds that hold atoms together.