g) covalent substances

Question 1

1.38 describe the formation of a covalent bond by the sharing of a pair of electrons between two atoms

Answer 1

1.38 describe the formation of a covalent bond by the sharing of a pair of electrons between two atoms

Question 2

1.39 - understand covalent bonding as a strong attraction between the bonding pair of electrons and the nuclei of the atoms involved in the bond

Answer 2

When non-metals share electrons, they are attracted by the nucleus. Since nucleus is positively charged it attracts negatively charged electrons.

Question 3

1.40 explain, using dot and cross diagrams, the formation of covalent compounds by electron sharing for the following substances:

Answer 3

2. chlorine
3. hydrogen chloride
4. water
5. methane
6. ammonia
7. oxygen
8. nitrogen
9. carbon dioxide
10. ethane
11. ethene
    - For the diagrams http://www.shawonnotes.com/index/section_1_principles_of_chemistry_igcse_chemistry/0-32

Question 4

1.41- understand that substances with simple molecular structures are gases or liquids, or solids with low melting points

Answer 4

In covalent bonds, the intermolecular forces are very weak. Because molecules are electrically neutral unlike ions. They have charges in proton and neutron which are very weak.

Question 5

1.42- explain why substances with simple molecular structures have low melting and boiling points in terms of the relatively weak forces between the molecules

Answer 5

In covalent bonds, the intermolecular forces are very weak. Because molecules are electrically neutral unlike ions. They have charges in proton and neutron which are very weak.

Question 6

1.43- explain the high melting and boiling points of substances with giant covalent structures in terms of the breaking of many strong covalent bonds

Answer 6

Giant covalent bond have strong intermolecular attraction. It need a lot of energy to separate them that is they have high melting and boiling point.