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Introduction to Chemistry and Laboratory Apparatus | Week 15 Topics1 Quiz
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Nature of Matter | Week 23 Topics1 Quiz
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Separation Techniques I | Week 31 Topic
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Separation Techniques II | Week 45 Topics1 Quiz
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Particulate Nature of Matter I | Week 55 Topics1 Quiz
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Particulate Nature of Matter II | Week 69 Topics1 Quiz
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Symbols, Formulae & Oxidation Number | Week 77 Topics1 Quiz
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Laws of Chemical Combination | Week 84 Topics1 Quiz
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Chemical Equation & Chemical Combination (Chemical Bonding) I | Week 94 Topics1 Quiz
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Chemical Combination (Chemical Bonding) II | Week 104 Topics1 Quiz
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Chemical Combination (Chemical Bonding) III & Shapes of Covalent Molecules | Week 113 Topics1 Quiz
Topic Content:
- Introduction – Covalent Molecules
- Linear Shape
- Tetrahedral Shape
- Angular Shape
- Trigonal Shape
- Trigonal Pyramidal Shape
- Trigonal Planar Shape
Introduction – Covalent Molecules:
In Covalent Molecules, atoms combine by sharing electrons.
Covalent molecules have a definite shape due to the fact that Covalent bonds are rigid and highly directional. However, the Ionic bondsAn electrovalent or ionic bond is formed when a metal atom transfers one or more electrons to a non-metal atom. Ionic or electrovalent compounds are those compounds which are formed by... More are not directional. Shapes of Covalent molecules are as follows:
1. Linear Shape:
All diatomic molecules are Linear in shape e.g. H2, Cl2, O2, N2. Other Compounds that have a Linear shape are CO, HCl, HF, CO2, SO2, etc. A linear molecule is a molecule in which atoms are deployed in a straight line, and the bond angle is 180°C.
The Linear shape of Hydrogen, Oxygen, Nitrogen, and Chloride:
(a) Hydrogen (H2)
(b) Oxygen (O2)
(c) Nitrogen (N2)
(d) Chloride (Cl2)
(d) Carbon (IV) Oxide (CO2)
2. Tetrahedral Shape:
This is a molecular shape that results when there are four bonds and no lone pairs around the central atom in a molecule. The atoms bonded to the central atom lie at the corners of a tetrahedron with a 109.5° angle between them.
The Covalent molecules that are tetrahedral in shape are methane (CH4), Tetrachloromethane (CCl4), Silicon tetrachloride (SiCl4), etc.
3. Angular Shape:
Angular Shape is also called V-shape. Water is the only covalent molecule that has an angular shape. The bond angle in water is 105°. A molecule of water has two pairs and two lone pairs of electrons. In a water molecule, the central atom is Oxygen.
4. Trigonal Shape:
Trigonal molecular shape results when there are three bonds around the central atom in a molecule. The bond angles are 120°.
There are two types of Trigonal Shape
a. Trigonal Pyramidal Shape
b. Trigonal Planar Shape
a. Trigonal Pyramidal Shape:
Trigonal pyramidal shape results when there are three bonds and one lone pair of electrons on the central atom in the molecule e.g. Ammonia (NH3) and Phosphine (PH3). In the Ammonia molecule, the three hydrogen atoms occupy the corners of the triangular base, with the lone pair of electrons occupying a large space at the apex. The bond angle between the two N-H bonds is approximately 107°.
b. Trigonal Planar Shape:
Trigonal Planar Shape results when a molecule has a central atom bonded to three surrounding atoms with no lone pair of electrons e.g. Phosphorus Chloride (PCl3), Aluminium Chloride (AlCl3), Boron trifluoride (BF3), Aluminium trihydride (AlH3), Sulphur (VI) Oxide (SO3), etc.
Theory Questions:
1. (a) List two forces of attraction that can exist between covalent molecules
(b) Name the type of Intermolecular force of attraction in the following:
(i) Iodine Crystals
(ii) Hydrogen Fluoride
(iii) Argon
View Answer2. (a) Give the reason why Hydrogen Fluoride is a liquid at room temperatureIf something is at room temperature, its temperature is neither hot nor cold. It is a range of air temperatures that most people prefer for indoor settings, usually considered to be... More, unlike Hydrogen Chloride
(b) Name the types of bonds within a water molecule and between water molecules.
View Answer3. (a) Explain the term Metallic Bonding
(b) State the type of chemical bond between Aluminium atoms in a sheet of Aluminium
(c) Mention three physical properties of Metal
View Answer4. Give two examples of each of the following Covalent molecules
(a) Linear Shape
(b) Tetrahedral Shape
(c) Trigonal Shape
(d) Trigonal Planar Shape
View Answer5. (a) Given the boiling points of the following Hydrid
| Hydride | Boiling Point |
| H2O | |
| H2S | |
| HF | |
| HCl |
State what is responsible for the high boiling point of H2O and HF
(b) Explain the following observations
(i) Mg has a higher melting pointThe temperature at which a solid changes its state to liquid at atmospheric pressure is called the melting point of that liquid. The melting point is usually defined as the point... More than Na
(ii) K is a better-reducing agent than Na
View Answer