Metals are electropositive elements because they tend to lose electrons easily. In chemical reactions, metals readily give away their outer electrons to form positive ions, making them good conductors of electricity and heat. This electron loss leads to the formation of cations, which contribute to the electropositive nature of metals.

This is a fundamental constant in chemistry that represents the number of atoms or molecules in one mole of a substance. (Option 4 is correct) Its value is approximately 6.022 x 10²³, and it is denoted by the symbol "N_A". Avogadro's number is a key concept in stoichiometry. The branch of chemistry deals with the quantitative relationships between reactants and products in chemical reactions.