Atomic Spectra One idea in early 20th century was that an electron (e-) traveled about the nucleus in an orbit. (planetary model)

Arrangement of Electrons in Atoms Electrons in atoms are arranged as LEVELS (n) SUBLEVELS (l) ORBITALS (ml)

Energy Levels n = 1 n = 2 n = 3 n = 4

Relative sizes of the spherical 1s, 2s, and 3s orbitals of hydrogen.

p Orbitals this is a p sublevel with 3 orbitals These are called x, y, and z There is a PLANAR NODE thru the nucleus, which is an area of zero probability of finding an electron 3py orbital

p Orbitals The three p orbitals lie 90o apart in space

d Orbitals d sublevel has 5 orbitals

The shapes and labels of the five 3d orbitals.

f Orbitals For l = 3, ---> f sublevel with 7 orbitals

How many electrons can be in a sublevel? Remember: A maximum of two electrons can be placed in an orbital. s sublevel p sublevel d sublevel f sublevel Number of orbitals Number of electrons

Electron Configuration Honors Chemistry Chapter 4

Electron Configuration The way electrons are arranged around the nucleus.

Three rules are used to build the electron configuration: Aufbau principle Pauli Exclusion Principle Hund’s Rule

Aufbau Principle Electrons occupy orbitals of lower energy first.

Pauli Exclusion Principle An orbital can hold only two electrons and they must have opposite spin.

Hund’s Rule In a set of orbitals, the electrons will fill the orbitals in a way that would give the maximum number of parallel spins. Analogy: Students could fill each seat of a school bus, one person at a time, before doubling up.

Aufbau Diagram for Hydrogen

Aufbau Diagram for Helium

Aufbau Diagram for Lithium

Aufbau Diagram for Beryllium

Aufbau Diagram for Boron

Aufbau Diagram for Carbon

Aufbau Diagram for Nitrogen

Aufbau Diagram