Electron Configurations - Chapter 3 Review

Ionization Energy

• Energy required to remove 1 mole of electrons electron from 1 mole of atoms of an element.

• kJ/mol

• Atoms are in a gaseous state.

3 Factors of Ionization Energy

• Size of nuclear charge or effective nuclear charge.

• Distance of valence electron from the nucleus.

• Shielding Effect.

Shielding Effect

When the full inner shells of an atom repel the outer shell, reducing the effective nuclear charge.

Nuclear Charge

The attractive force between the protons located in the nucleus and the electrons that surround it. 

Shell

• Principle Quantum Shell.

• Energy Level.

• Electron Shells.

Subshell

• Divisions of Shells

• s-subshell (2 electrons)

• p-subshell (6 electrons)

• d-subshell (10 electrons)

Orbitals

• A region of space where an electron is most likely to be found.

• Divisions of subshells.

• Each holds 2 electrons.

What is the shape and number of orbitals each subshell has?

• s-orbital; Spherical; 1 orbital.

• p-orbital; Dumbbell; 3 orbitals.

• d-orbital; A ring between 2 spheres; 5 orbitals.

Exceptions to the Electron Configuration

• Chromate [Cr] 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹ 

• Copper [Cu] 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹ 

• The 4s is not fully filled as the electron from the subshell moves to the 3d shell to make it more stable.

• Group 6 and Group 11 elements.

Aufbau’s Rule

• Electrons fill shells with the least energy.

• Energy increases as the Principle Quantum Number increases.

Pauli Exclusion Principle

• 2 electrons per orbital.

• Electrons in the same orbital experience Spin-Pair Repulsion.

Hund’s Rule

• Electrons will fill subshells by taking up empty orbitals first before pairing up.

• Electrons that are alone spin the same direction as all other lone electrons. 

How does the Ionization Energy change across a period?

• Increases

• Nuclear Charge increases

• Distance from Nuclear Charge is constant

• Shield Effect is constant

How does the Ionization Energy change down a group?

• Decreases significantly

• Distance from Nuclear Charge increases

• Shielding Effect increases

• These factors outweigh the nuclear charge increase

How does the Ionization Energy change when removing a lone electron from a subshell?

• Is lower

• Distance from nucleus is constant

• Shielding is constant

• Nuclear charge increases

• Why Boron has a lower Ionization Energy than Beryllium

How does the Ionization Energy change when an electron is in spin-pair repulsion?

• Decreases

• The extra repulsion helps to remove it.

• Why Oxygen has a lower Ionization Energy than Nitrogen.

Successive Ionization Energy

• Consecutive removal of 1 mole of electron from 1 mole of atoms of a particular element.

• Sudden increases indicate a change in subshells

• Increasing trend as effective nuclear charge increases while distance and shielding decreases.