If the oxidation number of an atom decreases, the atom has undergone oxidation. a. true b. false

Oxidation is a process when an atom, a group of atoms, or an ion loses electrons.

For example,

Cu⁰ > Cu⁺² + 2e⁻. This is an oxidation process.

As we can see an oxidation number was 0, and it became +2. The oxidation number is increased. Oxidation number of the atom, when an atom has undergone oxidation, increases.

So, answer is b.False.

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.