Structure of Atom Test - 44

The fundamental particles present in equal numbers in neutral atoms (atomic number 71 protons and electrons. There are 71 electrons and 71 protons. The number of neutrons may be same as (or different than) 71.

Any p-orbital can accommodate up to 6 electrons.
p-orbital has three sub-shells $$\displaystyle p_x$$, $$\displaystyle p_y$$ and $$\displaystyle p_z$$ each of which can accommodate 2 electrons.

 Atomic number is a whole number whereas atomic mass, atomic radius, and atomic volume can have fractional values. 

Atomic number of an element represents the number of protons in the nucleus. It is also equal to the number of electrons in neutral atom. The number of neutrons is equal to the difference between mass number and atomic number.
For example, for $$\displaystyle _{17}^{37}Cl$$, the atomic number is 17, the mass number is 37, there are 17, electrons, 17 protons and $$\displaystyle 37-17=20$$ neutrons.

Bohr advanced the ideal of stationary orbits. As long as an electron is revolving in an orbit it neither loses nor gains energy. Each stationary state is associated with definite amount of energy.

In Bohr's model, if the atomic radius of the first orbit $$\displaystyle r_1$$, then the radius of the fourth orbit will be $$\displaystyle 16 \times r_1$$.

The 37th electron will go into 5s sub-level.

According to aufbau principle, the correct order of energy of 4p and 5s-orbitals is $$\displaystyle 4p<5s$$

Aufbau principle:
In the ground state of the atoms, the orbitals are filled with electrons in order of increasing energy.

The 4p sub-energy level is at a lower energy than the 5s sub-energy level
For 4p, $$\displaystyle n=4$$ and $$\displaystyle l=1$$.  Hence, $$\displaystyle (n+l) = 4+1=5$$
For 5s, $$\displaystyle n=5$$ and $$\displaystyle l=0$$.  Hence, $$\displaystyle (n+l) = 5+0=5$$
As the value of $$\displaystyle (n+l)$$ for 4p orbital is same as that of 5s orbital, 4p orbital is filled before 5s orbital as 4p orbital has lower value of n than 5s orbital.

Note: If two orbitals have same value of $$\displaystyle (n+l)$$, then the orbital with lower value of n will be filled first.

According to aufbau principle, the correct order of energy of 3d,4s and 4p-orbitals is $$\displaystyle 4s<3d<4p$$

Aufbau principle:
In the ground state of the atoms, the orbitals are filled with electrons in order of increasing energy.

The 4s sub-energy level is at a lower energy than the 3d sub-energy level
For 3d, $$\displaystyle n=3$$ and $$\displaystyle l=2$$.  Hence, $$\displaystyle (n+l) = 3+2=5$$
For 4s, $$\displaystyle n=4$$ and $$\displaystyle l=0$$.  Hence, $$\displaystyle (n+l) = 4+0=4$$
As the value of $$\displaystyle (n+l)$$ for 4s orbital is less than that of 3d orbital, 4s orbital is filled before 3d orbital.

For 4p, $$\displaystyle n=4$$ and $$\displaystyle l=1$$.  Hence, $$\displaystyle (n+l) = 4+1=5$$
As the value of $$\displaystyle (n+l)$$ for 4p orbital is same as that of 3d orbital, 3d orbital is filled before 4p orbital as 3d orbital has lower value of n than 4p orbital.

Note: If two orbitals have the same value of $$\displaystyle (n+l)$$, then the orbital with the lower value of n will be filled first.

In the diagram of the option (D) are both Pauli exclusion principle and Hund's rule violated.
Pauli exclusion principle : Two electrons in an atom cannot have the same set of all four quantum numbers.
In the given diagram, two electrons in s subshell have same spin. This violets Pauli exclusion principle.

Hund's rule :  When several orbitals of equal energy (degenerate orbitals) are available, the electrons first fill all the orbitals singly before pairing in any of these orbitals.
In the given diagram, two electrons pair in one of the p subshells whereas the other p subshell is empty. This violates Hund's rule of maximum multiplicity.