GROUP 1

GROUP 1

1.       Alkali metals

2.       Exist naturally as compounds

3.       Elements: Lithium, sodium, potassium, rubidium, caesium and francium.

4.       General physical properties of lithium, sodium and potassium:

·         Exist as solid that have silvery and shiny surfaces at room temperature.

·         Low melting points and boiling point compared to other metals

·         Good conductors of heat and electricity

·         Low densities

5.       The Changes In the Physical Properties From Lithium, Sodium to Potassium

a)      Atomic size increases

Reason : Number of shells increases.

b)      Melting point and boiling point decreases

Reason : The increase in atomic size down the group causing the metal bond between atoms become weaker.

c)       Density increases

Reason : Increase in atomic mass more than the increase in atomic radius (volume of atom).

v  Show similar chemical properties (same number of valence electron in its outermost shell) but differ in reactivity.

v  Alkali metals donate one electron from its outermost occupied shell to form an ion with a charge of +1, achieving stable electron arrangement.

Example:

Na → Na⁺  + ē

      2.8.1      2.8

Chemical reaction for alkali metal

1.       Alkali metal + H₂O → Metal hydroxide solution + hydrogen gas

Example: 2Li(s) + 2H₂O(l) → 2 LiOH(aq) + H₂(g)

2.       Alkali metal + oxygen gas → Metal oxide

Example: 4Li(s) + O₂(g) → 2Li₂O(s)

3.       Metal oxide + water → Metal hydroxide solution

Example: Li₂O(s) + H₂O(l) → 2LiOH(aq)

4.       Alkali metal + chlorine gas

Example: 2Na(s) + Cl₂(g) → 2NaCl(s)

5.       Alkali metal + Bromine gas → Metal bromide

Example: 2K(s) + Br₂(g) → 2KBr(s)

** Halogens ( chlorine, bromine are always exist as diatomic molecules, thus the chemical formula are Cl2, Br2 )