Answer:
Helium
Explanation:
Helium is the least reactive element, since it is a noble gas with the smallest amount of valence rings.
Answer:
1
Explanation: that is the ratio
Answer:
protons
atomic number
Note: The same atomic number can be associated with several different values of atomic mass, but an element can have only 1 atomic number,
Assumes the shape and volume of its container
<span>particles can move past one another</span>
