S3.1 The periodic table: Classification of elements

Groups and Periods

Metals, Metalloids, and non-metals

Blocks in the periodic table

Alkali metals properties

• Forms alkaline solutions with water

• Soft

• Very reactive

Transition metal properties

• Transitionary behaviour between s-block and d-block elements

• Forms ions with difference charges

• High mp

• Good conductivity

Halogen properties

• Highly reactive

• Forms ionic salts with metals

Noble gas properties

• Colourless

• Inert

• Used for condensed electron configurations

Atomic radius

Distance from nucleus to outermost orbital, measured as half the distance between nuclei of 2 of the same atoms bonded together

Effective nuclear charge

Net positive charge from nucleus on the valence electrons by considering the screening effect of core electrons

Atomic radius trends

• Across a period, decreases because of increases effective nuclear charge

• Down a group, increases because higher energy level are further away from nucleus

Positive ion radii trend

• Atomic radii decrease

• Loss of electrons

• Increasing effective nuclear charge

Negative ion radii trend

• Atomic radii increase

• Gain of electrons

• Increased electron repulsion

Isoelectronic species

Molecules with same electron configuration

Ionisation energy

Energy required to remove 1 mole of electrons from 1 mole of gaseous atoms in the ground state

Ionisation energy general equation

Ionisation energy trend

Electron affinity

Energy released when 1 mole of electrons is added to 1 mole of gaseous atoms

Electron affinity trend

Electronegativity

Tendency of an atom to attract pairs of electrons in a covalent bond

Electronegativity trend

Metallic character and trend

Non-metallic character and trend

Reactions of Group 1 metals with water and trends

Reactions of Group 17 elements with halide ions

Acids

Form H⁺ ions in a solution

Bases

Forms OH^- ions in solution

pH scale

Concentration of H⁺ ions in a solution

Amphoteric

Substance that behaves as an acid and a base

Basic oxides

Acidic oxides

Ocean acidification

Acid rain

Oxidation state

Number assigned to an element showing the no. of electrons gained or lost or shared in a compound or ion

Ionic charge vs Oxidation state notations

• Ionic charge notation: 1+

• Oxidation state notation: +1

Rules for assigning oxidation state

Roman numerals are used for:

• Elements with variable oxidation states

• Oxyanions: Negatively charged polyatomic ions involving oxygen