Question

What are the quantum numbers for Bromine?

Answer 1

Quantum Numbers define the character of an electron in an energy specific orbital. They do not define an element.

Explanation:

4 Quantum Numbers define the character of an electron in an energy specific orbital.

According to the Pauli Exclusion principle, no two electrons can have the same set of 4 quantum numbers. This is significant in that elements with multiple electrons cannot have more than two in a single orbital.

Think of the set of Quantum Numbers for an electron as being a 'discrete energy window' for that electron and no other electron in the element's electron configuration can occupy the same energy window.

The 4 Quantum Numbers (QN) and what they describe are:

• Principle QN (`n`) => Defines Principal Energy Level
• Orbital QN (`l`); also known as Angular Momentum QN => Shape of Orbital
• Magnetic QN (`m_l`) => Orientation of orbital in 3 dimensions
• Spin QN (`m_s`) => the spin of the electron, up or down `pm 1/2`, respectively).

The 4 Quantum Numbers for the 'last' electron to fill a Bromine electronic configuration would be the electron in the half-filled `4p` orbital...

`=> (n, l, m_l, m_s) = (4, 1, {-1,0,+1}, -1/2) =>` represents only one of 35 electrons in the neutral Bromine atom.

We choose the set of `m_l` because the three `4p` orbitals are identical and thus there are three configurations that have the same energy:

`4p_x^2 4p_y^2 4p_z^(color(blue)(1))`

`4p_x^2 4p_y^(color(blue)(1)) 4p_z^2`

`4p_x^(color(blue)(1)) 4p_y^2 4p_z^2`