ELECTRON DIAGRAMSOrbital Notation, Noble Gas Notation, and Valence Electrons

Noble Gases

Method of representing electron configurations of noble gasesElements in the last column of the periodic

tableHave 8 electrons in their outermost orbitalExtremely stable

Nobel Gas Notation Recall, the electron configuration for Na is:

Na: 1s2 2s2 2p6 3s1

We can abbreviate the electron configuration by indicating the innermost electrons with the symbol of the preceding noble gas.

The preceding noble gas with an atomic number less than sodium is neon, Ne. We rewrite the electron configuration:

Na: [Ne] 3s1

Orbital Notation In electron configurations, we wrote the orbitals together

as one sublevel Example:

2px 2py 2pz all became the 2p sublevel

We do not get to see how the individual electrons line up

In orbital notations, each sublevel is written to show the electron’s spins in each direction

Orbital notation shows you where each specific electron is placed (in order) and what it’s “spin” is.

Reference Sheet

This reference sheet shows each orbital split apart into its 3 dimensional axes

Electron Configuration for Na Na, 11e-

1s2 2s2 2p6 3s1

We are now going to represent each electron as a “half arrow”

We must fill in the electrons as we did previously but show them using arrows on the orbital notation diagram

The first electron in an orbital is placed up (+1/2 spin)

1s

2s2px 2py 2pz

3px 3py 3pz

3s

Orbital Notation for Boron B, 5e- 1s2 2s2 2p1

1s

2s2px 2py 2pz

Orbital Notation Practice Helium

Boron

Carbon

Oxygen

Sodium

Manganese

Exceptions to Predicted Configurations Chromium

Incorrect: [Ar] 4s23d4

Correct: [Ar] 4s13d5

Copper:Incorrect: [Ar] 4s23d9

Correct: [Ar] 4s13d10

Elements in group 6 (s1d5) and group 11 (s1d10) have greater stability with half-filled and filled sets of s and d orbitals

Valence Electrons Only certain electrons determine the chemical

properties of an element

Valence Electrons:Electrons in the atom’s outermost orbitals – generally

those orbitals associated with the atom’s highest principal energy level orbitals (s and p)

Example:Sulfur contains 16 electrons6 electrons occupy the outermost 3s and 3p orbitalsTherefore, Sulfur has 6 valence electrons

Electron Dot Structures

Chemist often represent valence electrons in a short hand methodTermed Electron-Dot Structures

Structures consist of the element’s symbol surrounded by dots, representing the valence electrons