Period 3 Chemistry and Aluminium Extraction

Flashcards covering the structural properties, periodicity, chemical reactions, and industrial extraction of Period 3 elements and aluminium.

Giant Metallic Structure

The type of structure formed by sodium ($Na$), magnesium ($Mg$), and aluminium ($Al$) elements in Period 3.

Metalloid

The classification of silicon ($Si$), which forms a giant molecular structure where each atom is tetrahedrally bonded to four others by strong covalent bonds.

Simple Molecular Structure

Structures formed by phosphorus ($P$), sulphur ($S$), chlorine ($Cl$), and argon ($Ar$) consisting of discrete molecules joined by weak van der waal forces.

Screening effect

The shielding of the outer electrons from the nucleus, which remains constant across Period 3 as electrons are added to the same outer shell.

Effective nuclear charge

The net positive charge experienced by valence electrons; it increases from sodium to chlorine, causing the atomic radius to reduce.

Delocalized electrons

Electrons contributed to the charge cloud in metals; the number per atom increases from one to three from $Na$ to $Al$, increasing metallic bond strength.

Electronegativity

The power of an atom to attract bonding electrons towards itself, which increases from sodium to chlorine.

Electropositivity

The tendency of an atom of an element to lose its valence electrons to become positively charged; this decreases across Period 3.

Sodium Peroxide ($Na_2O_2$)

A pale yellow solid formed when sodium burns vigorously in excess air or oxygen.

Amphoteric

A substance, like aluminium oxide ($Al_2O_3$), that can react with both acids (forming salt and water) and hot concentrated bases (forming tetrahydroxoaluminate).

Sodium tetrahydroxoaluminate ($Na[Al(OH)_4]$)

A soluble complex formed when aluminium reacts with cold dilute sodium hydroxide solution.

Dimerization

The process where aluminium chloride ($AlCl_3$) forms $Al_2Cl_6$ via coordinate bonding when heated to $180^\text{o}C$.

Hexaaquaaluminium ion ($[Al(H_2O)_6]^{3+}$)

A soluble complex formed when aluminium ions attract water molecules; its high polarizing power weakens $O-H$ bonds, releasing $H^+$ and making the solution acidic.

Mixed Anhydride

Oxides like $ClO_2$ or $Cl_2O_6$ that dissolve in water to form a mixture of two different chloric acids.

Bauxite ($Al_2O_3.2H_2O$)

The main ore of aluminium, containing impurities such as silicon(IV) oxide ($SiO_2$) and iron(III) oxide ($Fe_2O_3$).

Cryolite ($Na_3AlF_6$)

A molten substance used to dissolve pure aluminium oxide during electrolysis to lower its melting point.

Passivity

The state of aluminium being unreactive with nitric acid due to the formation of a protective layer of aluminium oxide.

Halogen Carrier

The role of aluminium chloride ($AlCl_3$) in organic synthesis (Friedel-Crafts reactions) via the formation of the tetrachloro aluminate ion ($AlCl_4^-$).

Blue lake solution

The result of adding litmus solution to aluminium ions followed by dropwise aqueous ammonia until in excess.

Disulphur dichloride ($S_2Cl_2$)

A yellow liquid formed when sulphur is heated and reacts slowly with dry chlorine gas.