Question

The last entering electron in an element has quantum number n = 3, l = 2, m = + 2 and s = + 1 /2. The atomic number of the element will be​

Answer 1

Explanation:

Only one electron in a given atom can have the set of quantum numbers given in the question.

Explanation:

No two electrons in an atom can have the same set of quantum numbers.

The first quantum number is the principle quantum number , which is 

n=3

This means the electron is in the third energy level (shell).

The second quantum number, the angular momentum , is 

l=2

and means the electron is in the 

d sublevel (subshell).

The third quantum number, the magnetic quantum number , 

ml=2

represents one of the five 

3d orbitals.

Lastly, we have the spin quantum number , 

ms=+1/2

It indicates the direction of the spin of the electron.

Answer 2

The last entering electron in an element has the quantum numbers $n=3$, $l=2$, $m=+2$ and $s=+1/2$. The atomic number of the element will be​ 29.

Explanation:

• The principal quantum number is denoted by 'n'. It specifies the highest filled energy level or shell in which the last electron enters.
• As $n=3$, the shell in which the last electron enters is the third shell.
• The azimuthal quantum number is denoted by '$l$'. It specifies the subshell in which the last electron is filled.
• As $l=2$, the subshell in which the last electron goes is the d-subshell.
• The magnetic quantum number is denoted by 'm'. It specifies the orbital orientation of the last electron in space.
• As $m=+2$, the last electron enters the fifth d-orbital.
• The spin quantum number is denoted by 's'. It specifies the spin of the electron.
• As $s=+1/2$, the electron spin is upward.
• Therefore, the electronic configuration of the element can be given as:

        $\[1{s^2}\,2{s^2}\,2{p^6}\,3{s^2}\,3{p^6}\,4{s^2}\,3{d^9}\]$

• The total number of electrons according to this electronic configuration is 29. Therefore, the atomic number of the element is also 29.