Question

Use the periodic table to determine the electron configuration for aluminum (al) and arsenic (as) in noble-gas notation.

Answer 1

Answer: Electronic configuration of

1. Aluminium is $[Ne]3s^23p^1$

2. Arsenic is $[Ar]4s^23d^{10}4p^3$

Explanation: To write the electronic configuration of the elements in the noble gas notation, we first count the total number of electrons and then write the noble gas which lies before the same element.

• For Aluminium:

Atomic number = 13

Total number of electrons = 13

Noble gas which lies before this element is Neon (Ne).

Neon has 10 electrons, rest 3 electrons are filled in 3s and 3p sub-shells.

Electronic configuration of Aluminium becomes $[Ne]3s^23p^1$

• For Arsenic:

Atomic number = 33

Total number of electrons = 33

Noble gas which lies before this element is Argon (Ar).

Neon has 18 electrons, rest 15 electrons are filled in 4s , 3d and 4p sub-shells.

Electronic configuration of Arsenic becomes $[Ar]4s^23d^{10}4p^3$.

Answer 2

Al: [Ne] 2s2 2p1 

As: [Ar] 4s2 3d10 4p3