Answer:
Substances 1 and 2
Explanation:
an element only has 1 kind of atoms :3
Endothermic<span> Reaction??? </span>
The two main types of bonds formed between atoms are ionic bonds and covalent bonds. An ionic bond is formed when one atom accepts or donates one or more of its valence electrons to another atom. A covalent bond is formed when atoms share valence electrons.
