PRE MI UM ACT I VE- LE A RN IN G WO RK BOO K
Electron Configuration, Bonding &
Molecular Geometry
Atomic Structure, Lewis Structures, VSEPR, Hybridization & MO Theory
General Chemistry • Active-Learning Edition
How to use this workbook
1. Read the concept explanation. 2. Study the worked example. 3. Try the practice problems yourself.
4. Check your work against the Answer Key. 5. Revisit anything you missed.
, 1. Electron Configuration
● Electrons occupy orbitals in order of energy, following the Aufbau principle.
Steps for Configuration
● Count electrons: determine total electrons in the atom or ion.
● Fill orbitals in order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p.
● For ions: remove electrons from the highest principal quantum number (n) first. For transition metals,
remove from 4s before 3d.
IMPORTANT REMINDER
4s fills before 3d, but 4s electrons are also removed FIRST when forming cations.
✏ TRY IT YOURSELF
1. Write the electron configuration for Fe (Z = 26).
2. Write the electron configuration for Fe2+ — which electrons are removed first?
2. Atomic Radius and Isoelectronic Series
Term Definition
Atomic Radius Distance from the nucleus to the outermost electron shell.
For ions with the same electron configuration, more protons = smaller radius
Isoelectronic Comparison
(stronger pull on electrons).
Trend down a group Radius increases (more electron shells).
Trend across a period Radius decreases (more protons pull electrons closer).
Rules for comparison: anions > neutral atoms > cations (in size). More protons in an isoelectronic series →
smaller radius.
✏ TRY IT YOURSELF
1. Rank by size (largest to smallest): Na+, Mg2+, Al3+ (all isoelectronic with Ne).
2. Which is larger: K or Na? Why?
3. Ionization Energy & Electron Affinity
Term Definition
Energy required to remove an electron from a gaseous atom or ion. Increases up a
Ionization Energy
group and to the right across a period.
Energy change when an electron is added to a neutral atom to form a negative ion.
Electron Affinity
Generally becomes more negative (stronger) moving right across a period.
EXCEPTION TO REMEMBER
Electron Configuration, Bonding &
Molecular Geometry
Atomic Structure, Lewis Structures, VSEPR, Hybridization & MO Theory
General Chemistry • Active-Learning Edition
How to use this workbook
1. Read the concept explanation. 2. Study the worked example. 3. Try the practice problems yourself.
4. Check your work against the Answer Key. 5. Revisit anything you missed.
, 1. Electron Configuration
● Electrons occupy orbitals in order of energy, following the Aufbau principle.
Steps for Configuration
● Count electrons: determine total electrons in the atom or ion.
● Fill orbitals in order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p.
● For ions: remove electrons from the highest principal quantum number (n) first. For transition metals,
remove from 4s before 3d.
IMPORTANT REMINDER
4s fills before 3d, but 4s electrons are also removed FIRST when forming cations.
✏ TRY IT YOURSELF
1. Write the electron configuration for Fe (Z = 26).
2. Write the electron configuration for Fe2+ — which electrons are removed first?
2. Atomic Radius and Isoelectronic Series
Term Definition
Atomic Radius Distance from the nucleus to the outermost electron shell.
For ions with the same electron configuration, more protons = smaller radius
Isoelectronic Comparison
(stronger pull on electrons).
Trend down a group Radius increases (more electron shells).
Trend across a period Radius decreases (more protons pull electrons closer).
Rules for comparison: anions > neutral atoms > cations (in size). More protons in an isoelectronic series →
smaller radius.
✏ TRY IT YOURSELF
1. Rank by size (largest to smallest): Na+, Mg2+, Al3+ (all isoelectronic with Ne).
2. Which is larger: K or Na? Why?
3. Ionization Energy & Electron Affinity
Term Definition
Energy required to remove an electron from a gaseous atom or ion. Increases up a
Ionization Energy
group and to the right across a period.
Energy change when an electron is added to a neutral atom to form a negative ion.
Electron Affinity
Generally becomes more negative (stronger) moving right across a period.
EXCEPTION TO REMEMBER
