Question

Electronic configuration of deuterium is……………….
(A) $1{{s}^{2}}$
(B) $1{{s}^{1}}$
(C) $1{{s}^{2}}2{{s}^{1}}$
(D )$1{{s}^{2}}2{{s}^{2}}$

Answer 1

Isotopes are the elements those have the same atomic number but different mass numbers. Atoms are actually the number of protons present in the nucleus and we also know that for an atom the number of protons is always going to be equal to the number of electrons, it suggests that Isotopes will have the same number of electrons.

Complete answer:
Mass number= number of protons + number of neutrons
Hydrogen has three isotopes:
Protium: Since protium doesn’t have any neutron in its nucleus and only one proton it has so its mass number will be 1.
Deuterium: It has 1 neutron and 1 proton in its nucleus, so its mass number will be 2.
Tritium: It has 2 neutrons and 1 proton in its nucleus, so its mass number will be 3.
Clearly all three have the same number of protons and different mass numbers, therefore the number of electrons in their nucleus will also be the same.
Since all three isotopes have the same number of electrons, therefore their electronic configuration will be same and similar to the electronic configuration of the hydrogen atom.
Hydrogen’s atomic number is 1, so that one electron will be filled in $1s$ orbital.
Electronic configuration of hydrogen is $1{{s}^{1}}$
So electronic configuration of deuterium is

Correct answer is Option (B).

Additional information: Deuterium has an atomic weight of 2.014. It is a stable atomic species found in natural hydrogen compounds to the extent of about 0.0156 percent.

Note: Deuterium is used in the form of heavy water to slow down neutrons in nuclear reactors. It has its application in military, industrial and medicinal fields as well. In studying reaction mechanisms and stereochemistry of the products where deuterium labeled compounds are often used.