Modern Atomic Theory and ElectronsChapter 4 Section 3

Energy Levels

We already know that in Bohr’s model, electrons move at a constant speed around the nucleus like planets moving around the sun.

Each atom has energy. If an atom gains or loses energy, the energy of the electron can change.

Energy Levels- The possible energies that electrons in an atom can have.

An electron in an atom can move from one energy level to another when the atom gains or loses energy.

Think of Energy Levels Like a Staircase:

Just like you can’t stand in between stairs, electrons cannot exist between energy levels.

The bottom stair is like the lowest energy level, and each step up represents a higher energy level.

The distance between two steps represents the difference in energy between the energy levels

No two elements have the same set of energy levels.

Electron Cloud Model

*The movement of electrons between energy levels explains the light you see when fireworks explode!!!!!*

Electrons do in fact move more unpredictably then the planets in the solar system.

An electron cloud is a visual model of the most likely locations for electrons around the nucleus of an atom.

Electron Cloud Model

Atomic Orbitals

The electron cloud represents all the orbitals in the atom.

An orbital is a region of space around the nucleus where an electron is found.

An electron cloud is a good approximation of how electrons behave in their orbitals.

Atomic Orbitals

The lowest energy level has only one orbital, and higher energy levels have more than one orbital.

Each orbital can contain two electrons at most.

Energy Level Number of Orbitals Max. # of electrons

1 1 2

2 4 8

3 9 18

4 16 32

Electron Configurations

An electron configuration is the arrangement of electrons in the orbitals of the atom.

The most stable electron configuration is where the electrons have the lowest possible energies.

When an electron has the lowest possible energy, it is said to be in its ground state.