Ionic bonds are usually between a metal and a nonmetal and involve the transfer of electrons. Covalent bonds are typically between two nonmetals and involve the sharing of electrons.
Explanation:
When elements bond together ionically, they transfer their valence electrons to another element to satisfy the octet rule and create full shells of 8 electrons. Metals usually have low electronegativity and ionization energy and can more easily give up an electron to a nonmetal with higher electronegativity and ionization energy.
When two nonmetals bond, their electronegativities are close enough in magnitude that neither element can "claim" the valence electrons, so the electrons orbit back and forth between the elements in the bond.
An element is a mixture of two isotopes. One isotope has an atomic mass of 34.969 amu and an abundance of 64.88%. The other isotope has an atomic mass 36.966 amu.
The statement that the friend made is not true. most of the mass of the plant is from carbon. the carbon comes from carbon dioxide which is used during photosynthesis. the left over carbon from photosynthesis is used to to help the plant gain mass. there is a process for this which is called cellular respiration