Explain why neon is monatomic but chlorine is diatomic.

Explanation:

Neon is in group 8/0, which means that it has a full outer shell. Atoms react to get a full outer shell but as neon already has a full outer shell, it doesn't react and stays monatomic.

However, chlorine is in group 7, so it needs 1 more electron to complete its outer shell, two chlorine atom share one electron each with each other so they have full outer shells. This is why chlorine is diatomic.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.