s and p-Block Elements: Period 3 Properties and Trends

Vocabulary flashcards covering Period 3 element electronic structures, atomic radii trends, electronegativity, crystal structures, electrical conductivity, and melting/boiling point trends.

Period 3 Elements

The eight elements located in the third period of the Periodic Table, which include sodium ($Na$), magnesium ($Mg$), aluminium ($Al$), silicon ($Si$), phosphorus ($P$), sulphur ($S$), chlorine ($Cl$), and argon ($Ar$).

Electronic Structure of Sodium

The shortened electronic structure represented as $\text{[Ne]} \, 3s^1$.

Electronic Structure of Magnesium

The full electronic structure represented as $1s^2, 2s^2, 2p^6, 3s^2$, or shortened as $\text{[Ne]} \, 3s^2$.

Electronic Structure of Aluminium

The shortened electronic structure represented as $\text{[Ne]} \, 3s^2 \, 3p_x^1$.

Electronic Structure of Silicon

The shortened electronic structure represented as $\text{[Ne]} \, 3s^2 \, 3p_x^1 \, 3p_y^1$.

Electronic Structure of Phosphorus

The shortened electronic structure represented as $\text{[Ne]} \, 3s^2 \, 3p_x^1 \, 3p_y^1 \, 3p_z^1$.

Electronic Structure of Sulphur

The shortened electronic structure represented as $\text{[Ne]} \, 3s^2 \, 3p_x^2 \, 3p_y^1 \, 3p_z^1$.

Electronic Structure of Chlorine

The shortened electronic structure represented as $\text{[Ne]} \, 3s^2 \, 3p_x^2 \, 3p_y^2 \, 3p_z^1$.

Electronic Structure of Argon

The shortened electronic structure represented as $\text{[Ne]} \, 3s^2 \, 3p_x^2 \, 3p_y^2 \, 3p_z^2$.

Trend in Atomic and Ionic Radii

The atomic and ionic radii decrease across a period from left to right due to an increased effective nuclear charge pulling the electron cloud closer to the nucleus.

Electronegativity

A measure of the tendency of an atom to attract a bonding pair of electrons.

Pauling Scale

The standard scale used to measure electronegativity, where fluorine is assigned the maximum value of $4.0$ and caesium and francium are assigned the minimum value of $0.7$.

Electronegativity Trend Across Period 3

Electronegativity increases from sodium to chlorine because additional protons in the nucleus attract the bonding pair in the 3-level more closely against the same inner electron screening.

Argon Electronegativity Exclusion

Argon is excluded from electronegativity scales because it does not form covalent bonds.

Sodium Metallic Structure

An $8$-coordinated metallic crystal structure where each sodium atom is touched by $8$ other atoms, involving only a single $3s$ electron per atom in metallic bonding.

Magnesium and Aluminium Metallic Structure

A $12$-coordinated metallic crystal structure involving $2$ outer electrons per magnesium atom and $3$ per aluminium atom, resulting in more efficient atom packing and stronger bonding.

Giant Covalent Structure of Silicon

A network structure similar to diamond where atoms are held by strong covalent bonds, leading to high melting and boiling points.

Phosphorus Molecule ($P_4$)

A simple molecular structure made of $P_4$ units held together in solid or liquid form by weak van der Waals dispersion forces.

Sulphur Molecule ($S_8$)

A simple molecular structure consisting of $S_8$ rings that are larger than $P_4$ molecules, causing stronger van der Waals forces and higher melting and boiling points than phosphorus.

Chlorine Molecule ($Cl_2$)

A small diatomic simple molecular structure held by comparatively weak van der Waals dispersion forces, resulting in lower melting and boiling points than sulphur or phosphorus.

Argon Molecule ($Ar$)

A monoatomic simple molecular element held together in solid or liquid state strictly by weak van der Waals dispersion forces.

Electrical Conductivity in Period 3 Metals

Sodium, magnesium, and aluminium are good electrical conductors due to delocalised electrons free to move throughout the metal, with conductivity increasing from sodium to aluminium as more electrons are contributed.

Semiconductor (Silicon)

The electrical classification of silicon, which conducts electricity despite having a giant covalent diamond-like structure.

Van der Waals Dispersion Forces

Weak intermolecular attractions between simple molecular elements ($P_4$, $S_8$, $Cl_2$, $Ar$) in solid or liquid states that govern their melting and boiling points.