Electron ConfigurationsDon’t worry. Ya’ll got this! It’s not as difficult as it sounds!

So, this is what you’ll learn today:• You will learn that an atom is made up of mostly “empty space” • Electrons, and how they are positioned in the atom, determine how

that atom might react with other atoms• You will learn how to write an electron configuration for any element

on the Periodic Table• Lewis dot structures are another type of notation that will help you

visualize an atom’s valence electrons

Ok, get ready, cuz we’re about to do some Chemistry!

This is an atom.

This is a teeny, tiny nucleus.

This is the extremely vast and empty-ish electron cloud….

The electrons in an atom, because they are moving particles, have wave characteristics.

We can attempt to predict an electron’s location in an atom based on the wave functions of the electrons.• An atomic orbital is a 3-D

region around the nucleus that describes an electron’s probable location in the atom.

• The more dense the “cloud” is, the more likely the electron is there.

Principal Quantum Numbers (n)

• Indicate the relative sizes and energies of atomic orbitals.

• An n increases, the atomic orbital becomes larger, and the electron spends more time farther from the nucleus. The atom’s energy level increases.

• Because of this, n specifies the atom’s major energy levels, called principal energy levels

So, let’s recap…..• An atom’s electrons move around constantly and are NOT in fixed orbits like Neils Bohr thought.

• The electrons move because of the energy that is associated with that atom.

• We need to understand the arrangements of the electrons so that we can predict how the atom will react with other atoms.

Energy and Stability• Low-energy systems are more stable than high-energy

systems.• What do we mean by stable? • An atoms “wants” to be stable….. If it has high energy, it is less

stable. • So, electrons tend to arrange themselves in such a way that

gives the atom the lowest possible energy, which is called the ground-state electron configuration

There are seven principal quantum numbers (n)……

A different look to the Periodic Table

They just so happen to be arrangedin order in the Periodic Table

Each principal quantum number has sublevels associated with it• Remember this?

The sublevels are, in order of increasing energy:s, p, d and f