Question

An element having atomic number 83 belongs to
A. group 5, period 6
B. group 13, period 6
C. group 15, period 4
D. group 15, period 6

Answer 1

Hint: Bismuth is the element which has the atomic number of 83 and is represented by the symbol Bi. The group and period of any element is decided by the number of electrons as they tell us the number of shells present in the atom as well as the number of valence electrons of the atom.

Complete step by step solution:
-Bismuth atom has the atomic number 83. Atomic number gives the information about the number of protons as well as the number of electrons. So we can say that
Atomic number = no. of electrons = no. of protons
- There were 3 rules for electronic configuration.
1. (n+l) rule – It tells us in which subshell the electron goes first. Electrons enter in that subshell first which has the least value of n+l. This is because that subshell has the lowest energy level.
2. Hund’s rule of maximum multiplicity – Electrons are placed so as to obtain maximum multiplicity which is obtained by putting electrons of the same spin in different orbitals.
3. Pauli’s exclusion principle – It stated that no 2 electrons can exist with all 4 same quantum numbers.
-So, if we follow these rules, then we can see that the electronic configuration of Bismuth is
$\left[ Xe \right]4{{f}^{14}}5{{d}^{10}}6{{s}^{2}}6{{p}^{3}}$
-We see that there are 6 shells in the configuration which suggests that the period of this atom is the sixth period. The total number of electrons in the valence shell is 5. But the group of this atom is not 5 because it belongs to the d-subshell.
-The group of d-subshell atoms is decided by the total number of electrons in the valence shell and also the total number of electrons in the previous shell. The previous shell is 5d that has 10 electrons. So there are a total 10+5=15 electrons.

Thus Bismuth belongs to period 6 and group 15 and the correct option is D.

Note: Atomic number tells us about the number of protons and number of electrons while the atomic mass tells us about the number of protons and number of neutrons. If we know both the atomic mass and the atomic number, we can find all the number of protons, electrons and neutrons for any atom.