How would the composition of an atom change if both the atomic number and mass number each increase by one?
the atom would have 1 more neutron
the atom would have one more proton and electron
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the atom would have one more proton and one more neutron
the atom would have one more proton, one more neutron and one more
electron

The atom would have one more proton and electron.

Explanation:

An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.

All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if neutral atom has 6 protons than it must have 6 electrons. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.

Consider an atom X has 6 atomic number and 12 atomic mass. Atom gain one electron and one proton thus its atomic number will be

6+1 = 7

Atomic mass 12+1 = 13

It means by increasing one proton one electron atomic number and atomic weight both will increase by one.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.