Question

fusion
h proton neutron
h proton neutron
he protons neutrons
total protons neutrons
the number of protons an neutrons _ but the atoms have changed from _ to _.

Explanation:

Step1: Count protons in hydrogen atoms

Each hydrogen ($H$) atom has 1 proton. There are 2 hydrogen atoms, so total protons = 2.

Step2: Count neutrons in hydrogen atoms

Each hydrogen atom has 1 neutron. There are 2 hydrogen atoms, so total neutrons = 2.

Step3: Analyze helium atom

Helium ($He$) has 2 protons and 2 neutrons as a result of hydrogen - hydrogen fusion. The number of protons and neutrons remains the same before and after fusion in this case. The atoms have changed from hydrogen to helium.

Answer:

The number of protons and neutrons is 2 each. The atoms have changed from hydrogen to helium.