## Q. 4.4

Chromium, needed for maintenance of blood sugar levels, has four naturally occurring isotopes. Calculate the number of protons and number of neutrons in each of the following isotopes:

a.  $^{50}_{24}Cr$                      b.  $^{52}_{24}Cr$                      c.  $^{53}_{24}Cr$                      d.  $^{54}_{24}Cr$

## Verified Solution

In the atomic symbol, the mass number is shown in the upper left corner of the symbol, and the atomic number is shown in the lower left corner of the symbol. Thus, each isotope of Cr, atomic number 24, has 24 protons. The number of neutrons is found by subtracting the number of protons (24) from the mass number of each isotope.

 ANALYZE THE PROBLEM Given Need Connect atomic symbols for Cr isotopes number of protons, number of neutrons periodic table, atomic number

 Atomic Symbol Atomic Number Mass  Number Number of Protons Number of Neutrons a.  $^{50}_{24}Cr$ 24 50 24 26 (50 – 24) b.  $^{52}_{24}Cr$ 24 52 24 28 (52 – 24) c.  $^{53}_{24}Cr$ 24 53 24 29 (53 – 24) d.  $^{54}_{24}Cr$ 24 53 24 30 (54 – 24)