Solution:

For a gas with \( \gamma = \frac{C_p}{C_v} = 1.4 \):

1. Atomicity: For diatomic gases, \( \gamma = 1.4 \) (common for diatomic molecules like \(\text{O}_2\), \(\text{N}_2\), etc.).

2. Heat capacities:
- \( C_v = \frac{R}{\gamma - 1} = \frac{R}{1.4 - 1} = \frac{5}{2} R \).
- \( C_p = \gamma C_v = 1.4 \times \frac{5}{2} R = \frac{7}{2} R \).

Thus, the atomicity is diatomic, and the values of \( C_p \) and \( C_v \) are \( \frac{7}{2} R \) and \( \frac{5}{2} R \), respectively.