What are some similarties between hydrogen and deuterium

In the nucleus there are two main subatomic particles: The protons and the neutrons. The number of protons in the nucleus determines the element the atom is: 1 proton = hydrogen , 99 protons = Einsteinium , 6 protons = carbon etc.
The number of neutrons in the nucleus varies from atom to atom, even atoms of the same element. This causes the mass of the nucleus to vary slightly and can effect properties such as stability or type of nuclear decay. Atoms of the same element with different masses are called isotopes. They differ by the number of neutrons with the proton in te nucleus:
1 proton + 0 neutrons = 1 particle in the nucleus = hydrogen
1 proton + 1 neutron = 2 particles in the nucleus = deuterium
1 proton + 2 neutrons = 3 particles in the nucleus = tritium

Hope this helps

the catch is that the top numbers are atomic masses the bottom numbers are the numbers of protons and electrons in an uncharged atom. they are the number of that atoms as you would find them on the periodic table. further, the numbers on the left are used to determine the missing numbers on the right

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer

Hi; /c