Question

Using the periodic table, explain the difference between hydrogen, deuterium, and tritium - i.e. hydrogen-1, hydrogen-2, and hydrogen-3.
A) Allotropes vary in their number of protons - so they contain 1, 2, and 3 protons, respectively.
B) The atoms deviate in their number of photons - so they contain 1, 2, and 3 photons, respectively.
C) Isotopes differ only in their number of neutrons - so they contain 0, 1, and 2 neutrons, respectively.
D) These configurations diverge in their number of electrons - so they contain 1, 2, and 3 electrons, respectively.

Answer 1

C
These are all isotopes of Hydrogen and they differ from one another because of their different number of neutrons.

Answer 2

Answer: C) Isotopes differ only in their number of neutrons - so they contain 0, 1, and 2 neutrons, respectively.

Explanation: Isotopes are elements which have same atomic number but different mass number. Hydrogen has three isotopes named as hydrogen $_1^1\textrm{H}$ , deuterium $_1^2\textrm{H}$ , and tritium $_1^3\textrm{H}$.

Atomic number= number of protons = number of electrons (for neutral atom)

Mass number = number of protons + number of neutrons

Thus Number of neutrons = Mass Number - Atomic number

Thus number of neutrons in hydrogen with atomic number 1 and mass number 1 = 1 - 1 = 0

Thus number of neutrons in deuterium with atomic number 1 and mass number 2 = 2 - 1 = 1

Thus number of neutrons in tritium with atomic number 1 and mass number 3 = 3 - 1 = 2