Question

question 10. which two notations represent isotopes of the same element?
$_{7}^{20}n$ and $_{10}^{20}ne$
$_{7}^{14}n$ and $_{7}^{18}n$
$_{7}^{14}n$ and $_{10}^{17}ne$
$_{7}^{19}n$ and $_{10}^{16}ne$

Explanation:

Isotopes are atoms of the same element with the same atomic number (number of protons) but different mass numbers (sum of protons and neutrons). The atomic number is the sub - script in the notation. For an element to be the same, the atomic number must be identical. In the given options, only in the pair $^{14}_{7}\text{N}$ and $^{18}_{7}\text{N}$, the atomic number of nitrogen ($Z = 7$) is the same while the mass numbers ($14$ and $18$) are different.

Answer:

$^{14}_{7}\text{N}$ and $^{18}_{7}\text{N}$