The ideal bond angles marked 1, 2, and 3 in the molecule below are about , , and .

D= 109.5 degrees, 109.5 degrees, 120 degrees

Explanation:

The bond angle observed for any bond between two chemical species depends on the hybridization of the atoms.

However, for organic compounds, single bonds normally involve sp3 hybridized atoms with a bond angle of 109.5 degrees such as in the positions marked a and b.

However, a double bond is made of atoms in sp2 hybridized state with a bond angle of 120 degrees such as in c.

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