Write the IUPAC name of the compound having formula
`overset(3)CH_3 - underset(CH_3) underset(|) (""^2C )= overset(1)(C )H_2`

Explanation

There are 3 C atoms in the continuous chain containing double bound, therefore, the root word is .prop.. There is a double bond in a chain, therefore, the primary suffix is .ene.. There is methyl radical attached to carbon 2 of the chain, therefore, prefix is 2-methyl.
Thus, the IUPAC name of the given compound is
Root word + Root word + Primary suffix
2-Methyl + prop + ene = 2-Methylpropene