Which of the following represents a pair of isotopes?
A. $O _2, O _3$
B. ${ }_6^{14} C ,{ }_7^{14} N$
C. all are pairs of isotopes
D. ${ }_1^1 H ,{ }_1^2 H$
E. ${ }_{16}^{32} s,{ }_{16}^{32} s^{-2}$
Answer (1)
Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
Examine each pair to determine if they represent isotopes.
1 1 H and 1 2 H have the same atomic number but different mass numbers.
The pair of isotopes is 1 1 H , 1 2 H .
Explanation
Understanding Isotopes Let's analyze the options to identify the pair of isotopes. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. This means they have the same atomic number but different mass numbers.
Analyzing Each Pair
O 2 , O 3 : These are allotropes of oxygen, not isotopes. Allotropes are different structural forms of the same element.
6 14 C , 7 14 N : These are different elements (Carbon and Nitrogen) because they have different atomic numbers (6 and 7, respectively). Isotopes must have the same atomic number.
1 1 H , 1 2 H : Both have the same atomic number (1), so they are the same element (Hydrogen). They have different mass numbers (1 and 2), indicating different numbers of neutrons. Thus, they are isotopes.
16 32 S , 16 32 S − 2 : These are the same element (Sulfur) with the same atomic number and mass number, but one is an ion (charged). Isotopes are neutral atoms, so the difference in charge disqualifies them.
Identifying the Isotope Pair Based on the analysis, the pair that represents isotopes is 1 1 H , 1 2 H . They are both hydrogen atoms with the same number of protons (1) but different numbers of neutrons (0 and 1, respectively).
Final Answer Therefore, the correct answer is 1 1 H , 1 2 H .
Examples
Isotopes are used in various applications, such as carbon dating in archaeology and medicine for diagnostic imaging and cancer treatment. For example, carbon-14, an isotope of carbon, is used to determine the age of ancient artifacts. In medicine, iodine-131, an isotope of iodine, is used in the treatment of thyroid cancer. Understanding isotopes is crucial in these fields for accurate analysis and treatment.
