1. what are valence electrons? a) empty spaces in the innermost shell of an atom b) electrons in the outermost shell available for bonding c) empty spaces in the outermost shell of an atom d) electrons in the innermost shell available for bonding 2. an atom has an atomic mass of 56amu. the atom has 32 neutrons and 24 electrons. what is the number of the atom? a) 32 b) 24 c) 56 d) 112