Chemistry

Question 1

Electron configuration

Answer 1

refers to the distribution of electrons among the orbitals of an atom.

Question 2

Electrons filling orbitals

Answer 2

in order of increasing energy, starting from the lowest energy orbital (1s) and moving upwards. This is based on the Aufbau Principle.

Question 3

Electron filling orbital sequence

Answer 3

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p

Question 4

Hund’s Rule

Answer 4

Electrons will occupy empty orbitals of the same energy (degenerate orbitals) singly before pairing up.

Question 5

Pauli Exclusion Principle

Answer 5

No two electrons can have the same set of quantum numbers, so an orbital can hold a maximum of two electrons with opposite spins.

Question 6

Electron Configurations for Elements

Answer 6

Use the atomic number to determine how many electrons an atom has, and then distribute them according to the orbital filling order.

Question 7

Determine the Position of an Element in the Periodic Table from its Electronic Structure - Group Number

Answer 7

The group number corresponds to the number of electrons in the outermost shell.

Question 8

Determine the Position of an Element in the Periodic Table from its Electronic Structure - Period

Answer 8

The period corresponds to the highest energy level (principal quantum number, n) that contains electrons.

Question 9

Sodium (Na): 1s² 2s² 2p⁶ 3s¹

Period and Group -

Answer 9

Group 1 (1 electron in the outermost s orbital).
Period 3 (highest principal quantum number is 3).

Question 10

Blocks of the Periodic Table:
Elements are divided into blocks based on their electron configuration

Answer 10

d-block: Transition metals
S-Block
P-block

Question 11

Transition Metals

Answer 11

Transition metals have partially filled d orbitals, and their electron configurations typically end in d orbitals

Question 12

Ion Formation
Ions -

Answer 12

Ions form when atoms lose or gain electrons to achieve a full outer shell (usually achieving the same electron configuration as a noble gas).

Question 13

ions formation
metal -

Answer 13

lose electrons to form positive ions (cations)

Question 14

Non-metals

Answer 14

gain electrons to form negative ions (anions).

Question 15

Examples of Ion formation

Answer 15

Sodium (Na): Loses 1 electron to form Na⁺.
Configuration: Na⁺ = 1s² 2s² 2p⁶ (same as Neon).
Chlorine (Cl): Gains 1 electron to form Cl⁻.
Configuration: Cl⁻ = 1s² 2s² 2p⁶ 3s² 3p⁶ (same as Argon).

Question 16

Formulae of Ionic Compounds
Combine cations and anions to form neutral compounds.

Answer 16

Sodium Chloride (NaCl):
Na⁺ and Cl⁻ combine to form NaCl (ionic bond).
Calcium Oxide (CaO):
Ca²⁺ and O²⁻ combine to form CaO.

Question 17

Ionic Bonding

Answer 17

Occurs between metals and non-metals.
Involves the transfer of electrons from a metal to a non-metal, forming positive and negative ions

Question 18

Ionic Bonding properties

Answer 18

High melting and boiling points.
Conduct electricity when dissolved in water (as ions are free to move).
Brittle.

Question 19

Covalent Bonding

Answer 19

Occurs between non-metals.
Involves the sharing of electron pairs between atoms.

Question 20

Covalent Bonding Properties

Answer 20

Lower melting and boiling points compared to ionic compounds.
Do not conduct electricity.

Question 21

Metallic Bonding

Answer 21

Occurs in metals.
Delocalized electrons (free electrons) move throughout the lattice of metal cations.

Question 22

Metallic Bonding Properties

Answer 22

Conduct electricity.
Malleable and ductile.

Question 23

Intermolecular Forces

Answer 23

These are forces between molecules (not within molecules)

Question 24

Van der Waals Forces

Answer 24

Weak interactions between non-polar molecules.
Example: Between O₂ molecules.

Question 25

Hydrogen Bonding

Answer 25

Stronger than Van der Waals, occurs when hydrogen is bonded to electronegative atoms (N, O, F).
Example: Between H₂O molecules (responsible for water’s high boiling point).

Question 26

Prediction of Bonding Types

Answer 26

Ionic: Typically formed between metals and non-metals.
Covalent: Typically formed between two non-metals.
Metallic: Found in pure metals and alloys.
Intermolecular Forces: Found between molecules with covalent bonds.