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Apart from Tetrahedral Geometry, Another Possible Geometry for Ch4 is Square Planar with the Four H Atoms at the Corners of the Square and the C Atom at Its Centre. Explain Why Ch4 is Not Square Planar? - Chemistry

Apart from tetrahedral geometry, another possible geometry for CH4 is square planar with the four H atoms at the corners of the square and the C atom at its centre. Explain why CH4 is not square planar?

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Solution 1

According to VSEPR theory, if CH4were square planar, the bond angle would be 90°. For tetrahedral structure, the bond angle is 109°28′. Therefore, in square planar structure, repulsion between bond pairs would be more and thus the stability will be less.

Solution 2

Electronic configuration of carbon atom:

6C: 1s2 2s2 2p2

In the excited state, the orbital picture of carbon can be represented as:

Hence, carbon atom undergoes sp3 hybridization in CH4 molecule and takes a tetrahedral shape.

For a square planar shape, the hybridization of the central atom has to be dsp2. However, an atom of carbon does not have d-orbitalsto undergo dsp2 hybridization. Hence, the structure of CH4 cannot be square planar.

Moreover, with a bond angle of 90° in square planar, the stability of CH4 will be very less because of the repulsion existing between the bond pairs. Hence, VSEPR theory also supports a tetrahedral structure for CH4.

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NCERT Class 11 Chemistry Textbook
Chapter 4 Chemical Bonding and Molecular Structure
Q 21 | Page 130
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