Periodic table

Elements are arranged in the order of increasing atomic number

periods: number of occupied electron shells

groups: number of outermost shell/ valence electrons

they are noble gases and all are colourless gases that are very stable and inert because they have already had either duplet structure or octet structure, giving extra stability to the atoms.

• Form compounds with more than one charge • Form a variety of complex ions • Form coloured compounds • Act as catalyst when in either the form of elements or compounds

It is the s block and p block and they are regarded as representative or main group elements.

Group 1, group 2 and group 3 except boron are metals

shiny appearance, malleable, ductile and good electrical and thermal conductivity When reacted, they tend to lose electron(s) to form cations.

It is the d block and consists of transition elements

It is the f block and consists of lanthanides and actinides, which interrupt periods 6 and 7 on the Periodic table.

● Most of the elements in groups 4 to 7 are non-metals which lack distinctive physical properties that characterize them. ● Most of them are poor conductors of heat and electricity. ● When they react, they tend to gain electron(s) to form anions.

● They have properties in between those of metals and non-metals. ● Typical metalloids have a metallic appearance, but they are brittle and only fair conductors of electricity. ● Chemically, they mostly behave as non-metals. e.g. boron and silicon

• High electrical and thermal conductivity • High melting point • Malleable • Ductile

Lanthanides (Z = 58 to 71) are reactive, silver-coloured metals that tarnish when exposed to air. Actinides (Z = 89 to 103) are similar to typical metals but they are radioactive.

they are alkali metals, The elements in this group are shiny and silvery metals. They are generally soft and can be easily cut with a knife. Since they are very reactive, they should be stored in paraffin oil (a non-aqueous solvent) to prevent them from contact with air and moisture / water.

They are called alkaline earth metals, they show similar properties (shiny, silvery, soft, cut with knife, paraffin oil, prevent moisture and air) to those in group 1 but less reactive Denser and harder than group 1 metals

Reactivity of group 1 and 2 metals increases down the group, because of the increasing trend of atomic radius.

half of the distance between the nuclei of two neighbouring atoms

It refers to the distance from the nucleus to the outermost shell/valence electrons of the atom.

● Going down these two groups, the number of occupied electron shells of the atoms increases. ● The electrostatic force of attraction between the nucleus and the outermost shell electrons becomes weaker. ● Less energy required to remove this outermost shell/valence electron

This energy is referred as ionisation energy (I.E.), which is the minimum amount of energy required to remove one mole of electrons from one mole of gaseous atoms at ground state.

Equation: X (g) → X+ (g) + e-

they are called halogens and the elements in this group are all poisonous and reactive non-metals. They have different colour and physical states under ambient conditions

fluorine : pale green gas chlorine : pale green gas bromine : reddish brown liquid iodine : black solid