Rossita Radzak : SASER

CHEMICAL BOND (a) Group 1 elements react with Group 17 elements to produce compounds that have high melting points. (4 marks)

The points are: Ionic compound produced Because involve metal and non metal elements Metal atom donates valence electron to form positive ion, non metal atom accepts

electron to negative ion. The oppositely charged ions are held together by strong electrostatic force More heat energy is needed to overcome the force of attraction.

Formation of ionic compound (metal and non metal) Sample answer:

1. Electron arrangement of atoms ( Na , 28.1 ; Cl 2.8.7 )/ valence electrons 2. To achieve stable / octet electron arrangement 3. Atom ( Na) releases electron to form sodium ion, Na+ 4. Half equation ( Na Na+ + e) 5. Atom (Cl) gain / accept electron to chloride ion, Cl- 6. Half equation ( Cl + e Cl- ) 7. Oppositely charged ion, Na+ & Cl- are attracted to one another by strong electrostatic

force of attraction to form ionic compound, NaCl 8. Diagram

Formation of covalent compound (nonmetal) 1. electron arrangement of the atom /valence electrons 2. to achieve stable /octet electron arrangement 3. atom (Carbon) contribute 4 electrons while (H) atom contribute 1 electron (for sharing). 4. one ( Carbon ) atom share 4 pairs of electrons with 4 (H) atoms to form covalent

compound , CH4 / ratio 5. diagram

Compare the physical properties of covalent and ionic compound

Covalent compound Ionic compound Melting and boiling

- low Reason: - consist of molecules - weak inter molecular forces - less energy needed to overcome the weak forces

- high Reason: - consist of oppositely charged ions - The ions are held together by strong electrostatic forces. - More heat energy needed to overcome the strong forces.

Electrical conductivity

- consist of molecules -does not conduct electricity

- consist of oppositely charged ions - conduct electricity in molten and aqueous solution. - in molten and aqueous solution, ions can move freely.