Answer: Electrons
Explanation: Atoms are made up of electrons, protons and neutrons. Protons and neutrons are located in the nucleus while electrons are located outside the nucleus where they revolve round the nucleus in their orbitals. Electrons are involved in chemical reactions.
During chemical bonding, a metal atom transfers its valence electrons to a non-metal atom. In this type of bond, the metal atom losses electron while the non-metal atom gains electron. The metal atom losses electron to form a positively charged ion and attains a stable octet structure while the non-metal atom gains electron to form negatively charged ion and attains a stable duplet or octet structure. This type of bond is called ionic bond or electrovalent bond.