Question #8510a

1 Answer
Oct 5, 2017

Aufbau Principle is one of the pillars of the Quantum Theory. Let's see what it means :)

Explanation:

Aufbau Principle is related to atomic orbitals. It states that, "when a certain atom is in it's ground state or lowest energy state, electrons enter the atomic orbitals in a sequence from low energy orbitals to high energy orbitals".

Now, the relative energy of an atomic orbital is given by the following expression:

color(green)(E=n+l). larr where, color(red)("n") is the Principle Quantum number & color(blue)("l") is the Azimuthal Quantum number.

Now, we have got color(red)(7) Principle Quantum numbers and color(blue)(4) Azimuthal Quantum numbers.

Now, the four Azimuthal quantum numbers are :
o.0 (s).
o.1 (p) .
o. 2(d).
o. 3(f).

Now, more the color(red)("n+l") value higher the magnitude of energy of the atomic orbital.

An additional knowledge: if color(blue)(""l"") of two atomic orbitals are same, the atomic orbital with higher color(red)(""n"") value is assumed to have higher energy.

Accordingly, all the atomic orbitals are arranged according to the increasing order of their energies & electrons enter accordingly rarr

color(red)(1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p)

Hope it Helps :)