A student began to read the chart above and did not understand how these elements can have several different forms, but still be the same element. She knows where to find
Hydrogen on the periodic table of elements, but is confused about why these are considered
isotopes. Using your periodic table and referring to the data above, what is the best
response to this situation?

Recall the following:

• Hydrogen is Hydrogen 1
• Deuterium is Hydrogen 2
• Tritium is Hydrogen 3

A. Hydrogen, Deuterium, and Tritium are all isotopes of hydrogen. They each
have an atomic number of 1, because they have 1 proton. Hydrogen has
neutrons, Deuterium has 1 neutron, and Tritium has 2 neutrons.

B. Hydrogen, Deuterium, and Tritium are all isotopes of hydrogen. They each
have an atomic number of 1, because they have 1 proton. Hydrogen has
1 neutron, Deuterium has 2 neutrons, and Tritium has 3 neutrons.

C. Hydrogen, Deuterium, and Tritium are all different elements. They are giver
different names, because they have different atomic masses but the
same atomic numbers.

D. Hydrogen, Deuterium, and Tritium are all different elements. They are give
different names, because they have different atomic numbers and
different atomic masses.