Periodicity (Period 3 Elements) - Inorganic

Vocabulary flashcards covering the periodicity of physical and chemical properties of Period 3 elements, including atomic/ionic radii, structure types, and reactions with oxygen, chlorine, and water.

Atomic Radius

The distance from the nucleus to the outermost electrons, which decreases across a period due to increasing nuclear charge and little change in the shielding effect.

Shielding Effect

The reduction in the nuclear charge on the electron cloud due to the presence of inner shells of electrons; there is little change in this effect across Period 3.

Isoelectronic Series

A series of ions (such as $Na^+$ to $Si^{4+}$ and $P^{3-}$ to $Cl^-$) that have the same number of electrons, where ionic radius decreases as the proton number increases.

Giant Metallic Structure

The structure of Na, Mg, and Al characterized by metallic bonds between positive metal cations and a 'sea' of delocalised electrons.

Giant Molecular Structure

The structure found in Silicon ($Si$) and Silicon Dioxide ($SiO_2$) where atoms are held together by strong covalent bonds, resulting in high melting points.

Simple Molecular Structure

The structure of P, S, Cl, and Ar where molecules or atoms are held by weak instantaneous dipole-induced dipole forces.

Instantaneous Dipole-Induced Dipole Forces

Weak intermolecular forces whose strength depends on the number of electrons in a molecule, which increases with relative molecular mass.

Semi-conductor

A material like Silicon ($Si$), also known as a metalloid, which has electrical conductivity between that of a conductor and an insulator.

$$Al_2Cl_6$$

The dimer form of Aluminium Chloride ($AlCl_3$) that exists in the vapour phase.

Oxidation Number

A number representing the charge an atom would have if all bonds were ionic; the maximum value for Period 3 elements corresponds to their group number.

Amphoteric Oxide

An oxide, such as $Al_2O_3$, that can react with both acids and alkalis.

Basic Oxide

Metal oxides like $Na_2O$ and $MgO$ that react with acids to form salts and water, producing alkaline solutions in water.

Acidic Oxide

Non-metal oxides such as $SiO_2$, $P_4O_{10}$, $SO_2$, and $SO_3$ that react with alkalis to form salts and water.

Chlorine Reaction with Sodium

The reaction $2Na + Cl_2 \rightarrow 2NaCl$, which burns with a bright yellow flame and forms a white solid.

Hydrolysis of $AlCl_3$

The reaction of Aluminium Chloride with water to produce an acidic solution ($pH = 3$) and white fumes of $HCl$ gas due to the high charge density of the $Al^{3+}$ ion.

Charge Density

The ratio of an ion's charge to its volume ($\text{charge density} = \frac{\text{charge}}{\text{volume}}$), which determines the extent to which an ion polarizes water molecules.

Phosphonic Acid

Common name for $H_3PO_3$, which is formed when Phosphorus Trichloride ($PCl_3$) reacts with water.

Diagonal Relationship

Similarities in chemical properties between certain elements in Period 2 and the element diagonally below them in Period 3, such as Li and Mg or Be and Al.