Question

What is the shape of $\text{C}{{\text{H}}_{4}}$?
(a) Pyramidal
(b) Trigonal planar
(c) Linear
(d) Tetrahedral

Answer 1

Hint: The methods by which one can elucidate the shape of molecules are through the use of VSEPR theory. We can calculate the total bond pair of the molecule, after which geometry and shape can be predicted.

Complete step by step solution:
VSEPR stands for Valence Shell Electron Pair Repulsion theory. This theory is used to predict the shape of the molecules in a systematic way by using the number of electron pairs to determine the shape of the molecules.
Carbon is in group 4, and so has 4 outer electrons. It is forming 4 bonds to hydrogen, adding another 4 electrons-8 altogether, in 4 pairs. Because it is forming 4 bonds, these must all be bonding pairs.
Four electron pairs arrange themselves in space in what is called tetrahedral arrangement. A tetrahedron is a regular triangularly-based pyramid. The carbon atom would be at the centre and the hydrogen at the four corners. All the bond angles are ${{109.5}^{\text{o}}}$.

$\text{C}{{\text{H}}_{4}}$
Central atom	Carbon
Valence electron on central atom	4
4 Hydrogen atom (contributing 1 electron each)	4
Total	8
Divide by 2	4
Shape as per VSEPR Theory	Tetrahedral

Shape:
 

Hence, the correct option is (d) tetrahedral.

Note: It is important that you understand the use of various sorts of line to show 3-dimensional arrangement of the bonds. In diagrams of this sort, an ordinary line represents a bond in the plane of the screen or paper. A dotted line shows a bond going away from you into the screen or paper. A wedge shows a bond coming out towards you.