Electron Arrangement or

Electron Configuration

Electron Arrangement/Configuration

• modern chemistry changed some of Bohr’s ideas

• each energy level is divided into sublevels which are called orbitals

orbitals are s, p, d, & f and all have various shapes

Orbital the region of high probability of finding an electron

• each orbital can hold only two electrons• s orbitals are spherical in shape

compare the 1s orbital to the 2s orbital• p orbitals are dumbbell shaped

specifically, there are 3 p orbitals differentiated

by the labels px, py, & pz

For example, 3s2, 3 = energy level

s = type of orbital2 = number of electrons (in that orbital)

s and p orbitals

• Sublevel s is lowest in energy followed by p, then d, then f

• s sublevel can hold a maximum of 2 electronsp sublevel can hold a maximum of 6 electronsd sublevel can hold a maximum of 10 electronsf sublevel can hold a maximum of 14 electrons

• Some energy levels do not have all the sublevels

• 1st energy level – s orbital only 1s• 2nd energy level – s & p orbitals 2s & 2p• 3rd energy level – s, p, & d orbitals 3s, 3p, &3d

• 4th energy level – s, p, d, & f orbitals 4s, 4p, 4d, &

4f

• The process of organizing electrons in atoms from the orbital with the lowest energy to the orbital with the highest energy is called electron configuration/arrangement.

• Electrons are not organized or “build up” in order of energy level and sublevels

i.e. 4s come first then 3d

• Use the following diagram to help remember the order in which orbitals fill:

7s 7p6s 6p 6d5s 5p 5d 5f4s 4p 4d 4f3s 3p 3d2s 2p1s

Examples: Write the electron configurations for the following:

(always determine the total number of electrons involved then use the helpful tool to write out

each orbital in order of building up)

H

O

K

Make Note:

• The periodic table is divided according to the filling order of sublevels

• Can relate a specific sublevel to a part of a row in the periodic table

• Creates trends in how elements react

Periodic Table