PLEASE HELP CHEMISTRY ASAP

Not positive

NaCl is an IONIC compound and readily dissociates in water  But stable as the solid 'salt'

H2O is a covalent polar compound but is relatively stable

Argon is a noble gas....noble gases (neon, krypton etc)  are very UN-reactive because they are stable

Clorine atoms are very reactive...chlorine is almost never found in a pure state, but rather as a compound with other elements

    So I will say Chlorine atom is the least stable config.