Chapter 2 - Atoms, Molecules, and Ions - Questions and Exercises - Exercises - Page 84: 2.44

Atomic mass = 63.55 u. The element is copper (Cu).

Atomic mass of the element = $(\frac{30.83}{100}\times64.9278u)+(\frac{100.00-30.83}{100}\times62.9396u)$ = 63.55u The element with atomic mass 63.55 u is copper and its symbol is Cu (Refer Periodic Table)