Chapter 2
Q. 2.1
ⓐ An isotope of cobalt (Co, Z = 27) is used in radiation therapy for cancer. This isotope has 33 neutrons in its nucleus. What is its nuclear symbol?
ⓑ One of the most harmful components of nuclear waste is a radioactive isotope of strontium, _{38}^{90}Sr; it can be deposited in your bones, where it replaces calcium. How many protons are in the nucleus of Sr-90? How many neutrons?
ⓒ Write the nuclear symbol for the element used in diagnostic bone scans. It has 31 protons and 38 neutrons.
ⓐ
| ANALYLSIS | |
| Z (27); number of neutrons, n (33) | Information given: |
| nuclear symbol | Asked for: |
STRATEGY
1. Note that Z stands for the atomic number or the number of protons p^{+}.
2. Recall that a nuclear symbol is written _{Z^A}X where A stands for the number of neutrons (n) plus protons (p^{+}).
ⓑ
| ANALYLSIS | |
| nuclear symbol: _{38}^{90}Sr | Information given: |
| p^{+}; n | Asked for: |
ⓒ
| ANALYLSIS | |
| p^{+} = 31; n = 38 | Information given |
| identity of the element | Information implied: |
| nuclear symbol | Asked for: |
Step-by-Step
Verified Solution
ⓐ
nuclear symbol Z = p^{+} = 27; A = p^{+} + n = 27 + 33; _{Z}^{A}Co = _{27}^{60}Co
ⓑ
| protons | Z = p^{+} = 38 |
| neutrons | A = p^{+} + n = 90; 90 = 38 + n; n = 90 – 38 = 52 |
ⓒ
| nuclear symbol | Z = p^{+} = 31 (placed on bottom left of element) A = p^{+} + n = 31 + 38 = 69 The element (X) is gallium identified by its atomic number Z. nuclear symbol: _{Z}^{A }X = _{31}^{69}Ga |