Quantum Numbers And Electronic Configuration Examples And Worksheet

Quantum Numbers And Electronic Configuration Examples And Worksheet - F. Scullion Page 3

The Aufbau (building up) Principle for Electronic Configuration.

In the so-called “ground state” of an atom the electronic configuration

generally follows this principle.

According to this principle, electrons enter into states in order of the

states increasing energy.

Electrons are reluctant to pair up with another in the same atomic orbital

(due to repulsions) and to go to a higher energy level than is necessary.

When faced with the need to do one or other, they generally settle for

pairing up with opposite spins, rather than go into the next highest

energy level.

Complete for Oxygen (8)

Complete for Sodium (11)

Exceptions to this rule include Chromium (4s

) and Copper (4s

)

These result because it requires less energy to maintain an electron in a

half-filled or filled d sublevel than paired in the s sublevel below.

s p d and f block elements

Assigned according to the oribtal getting the final electron.

Colour in the chart below to show each of these blocks.

Quantum Numbers And Electronic Configuration Examples And Worksheet - F. Scullion Page 3