Chemistry - Structure 1.3

Pauli Exclusion principle

Only two electrons can occupy the same atomic orbital and those electrons must have opposite spins

Aufbau Principle

The lowest available energy orbitals fill before higher energy orbitals do

Hunds Rule

every degenerate orbital in a sublevel is singly occupied before any orbital is doubly occupied. All electrons in single occupied orbitals have the same spin

Exceptions to Aufbau Principle

Transition metals when forming ions lose their 4s electrons first. Copper and Chromium fill their 3d orbital before they fill their 4s orbital

Why do Copper and chromium not follow the aufbau principle

it helps them be more stable

Ionization Energy

The energy required to remove one mole of electrons from one mole of an atom in its gaseous state

Why does the first ionization energy decrease down a group

The number of sublevels increases, which means there is a greater shielding effect and therefore less energy is required to remove electrons from the outermost sublevel

Why does the first ionization energy increase across a period

Number of protons increases, whichincreases the nuclear charge. Shielding effect remains constant because the number of inner electrons does not change. Therefore more energy is required to remove outermost electrons

General Trend of ionization energy

increases across a period, decreases down a group

Sucessive ionization energies

It requires more energy to remove the second and succesive electrons from an atom, because the number of protons exceeds the number of remaining electrons while electron-electron repulsion decreases

Why do gaseous atoms produce line spectra instead of continuous spectra?

Electrons in atoms occupy discrete energy levels, so electron transitions between these levels consume or emit specific quanta of energy. Each quantum of energy corresponds to a photon of specific wavelength

Atomic orbitals

s, p, d & f orbitals. They each have specific shapes and no. of electrons that can occupy them

s orbital

Spherical shape and can hold up to 2 electrons

p orbital

dumbbell shaped and can hold up to 6 electrons