Answer
\begin{matrix}
& Symbol & Atomic \space number & Mass \space number \\
a. &H & 1 & 3\\
b. &Cr & 24 &52 \\
c. &Ca & 20 & 42 \\
d. &Ta & 73 & 182 \\
\end{matrix}
Work Step by Step
1. To determine the atomic number, consult a periodic table (Figure 4.9, page 102).
a. Hydrogen (H): 1
b. Chromium (Cr): 24
c. Calcium (Ca): 20
d. Tantalum (Ta): 73
2. Use this equation to calculate the mass number:
Mass number = Number of neutrons + Number of protons
Remember: Number of protons = Atomic Number
a. 2 + 1 = 3
b. 28 + 24 = 52
c. 22 + 20 = 42
d. 109 +73 = 182
