1. Rossita Radzak SASER
Periodic Table of Elements
1. Explain the following statements, referring to the electron arrangement of the elements.
(a) The elements of Group 18 are uncreative and exist as monoatomic particles (3 marks)
The points are:
Stable electron arrangement. ( duplet / octet )
No tendency to donate, accept, share electrons
Remain as individual particles
(b) The reactivity of group I elements increases down the group, whereas the reactivity
of Group 17 elements decreases down the group. (12 marks)
The points are:
Change in proton number ( increases )
Change in number of electrons and electron filled shells ( increases )
Change in atomic size/radius/diameter ( increases )
Strength of electrostatic attraction between nucleus and valence electron ( decreases )
Tendency to release or attract / accept electrons
Reactivity increases/decreases
(2) Explain how the melting point of group 1 elements change down the group.( 4 marks)
decreases gradually
Reason
atomic size increases
metallic bonding between the atoms become weaker
less energy is required / needed to overcome this metallic bonding.
(3) Chemical properties of element in group 17
* Reaction with water
Cl2 + H2O HCl + HOCl
Reaction with sodium hydroxide
Cl2 + 2NaOH NaCl + NaOCl + H2O
Reaction with iron
3Cl2 + 2Fe 2FeCl3 (brown solid)
Chlorine gas
To Soda lime
produce Iron wool
Cl2 HCl ( cons) Sodium hydroxide solution
KMnO4(s)
(4) Across period 3, atomic radius (atomic size) decreases / electronegativity increases. Explain.
- Proton number increases by one unit
- The number of valence electrons in each atom increases
- Positive charge of the nucleus increases thus nuclei attraction on valence electron increases
- Atomic radius (atomic size) decreases
- Tendency to receive electron increases thus electronegativity increases
