What is the atomic number of an element based on

The atomic number is the number of protons in the nucleus of an atom . The number of protons define the identity of an element

hope this

explanation:

covalent bonds

consist of pairs of electrons shared by two atoms, and bind the atoms to fixed orientation and requre high energies to break them

ionic bonds

when two atoms differ considerably in their electronegativity, then one of the atoms will lose its electron to the other atom. this results in a positively charged ion(cation) and a negatively charged ion (anion)

i think it is d. e because the next one is igneous.