atomic orbitals and electron filling

what happens to energy levels as n increases

get closer together and converge at n = ∞ where there is zero energy. more negative energy = more stable.

what is a probability density plot

what are the problems with it?

exponential curve showing probability density against distance from the nucleus

problems: never hits zero, probability highest at r = 0 ie at the nucleus (but there are no electrons found here).

what was developed to avoid the problems with a probability density plot

a radial probability plot, which shows the probability against distance as well, but absolute probability is not plotted - instead it is normalised (see 1205)

radial probability plot for 2s orbitals

radial probability plot for 3s orbitals

what is orbital penetration and why does it occur

penetration power of the orbitals?

p-orbitals have a zero-point at the nucleus but s-orbitals don’t.

electron penetration is the electron’s probability density near the nucleus, and so as s orbitals have a higher density near the nucleus, they are penetrating the nucleus of the atom more than the p orbitals. this results in them having lower energy.

penetration power: s > p > d > f

name the 3 rules for electron distribution within orbitals

1. Aufbau Principle

2. Pauli’s Exclusion Principle

3. Hund’s Rule of Maximum Multiplicity

what is the aufbau principle

orbitals are filled with electrons in order of increasing energy

what is pauli’s exclusion principle

no two electrons in the same atom can have the same set of four quantum numbers, so if two electrons occupy the same atomic orbital, they must have different spin quantum numbers. these two electrons are said to be spin-paired.

what is hund’s rule of maximum multiplicity

electrons occupy degenerate orbitals singly before pairing up