Answer:
Number of neautrons
Explanation:
Atoms from two different elements may have the same number of neutrons, but never the same number of protons. The number of protons is unique to the element and represents the atomic number. (sorcastic.org)
6 months with no sunrise and the other 6 without a sunset, at some places on Earth, are the result of the orientation of Earth's axis.
Answer:
the hydrogen filled balloon is denser than the air filled balloon