Some atoms are exceptions to the octet rule by having an expanded octet. which characteristic is needed for an atom to have an expanded octet? the atom has empty d-orbitals. the atom has more than eight valence electrons before bonding. the atom has empty p-orbitals. the atom has fewer than eight valence electrons after bonding.

a graduated cylinder.

explanation:

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.