1. Draw the Structure:

* Start with propane: A three-carbon chain (CH3-CH2-CH3)

* Add the methyl groups: Two methyl groups (CH3) are attached to the second carbon.

2. Count the Hydrogens:

* The central carbon: Has two hydrogens attached (CH).

* Each terminal carbon: Has three hydrogens attached (CH3).

* Each methyl group: Has three hydrogens attached (CH3).

Total: 12 Hydrogen atoms

3. Types of Hydrogens:

* Primary (1°): Hydrogens attached to a carbon bonded to only one other carbon. There are 9 primary hydrogens in 2-dimethylpropane.

* Tertiary (3°): Hydrogens attached to a carbon bonded to three other carbons. There are 3 tertiary hydrogens in 2-dimethylpropane.

Therefore, 2-dimethylpropane has 12 hydrogen atoms, 9 of which are primary and 3 of which are tertiary.