A chemical bond is the attraction force between atoms (covalent bond) or between oppositely charged ions (ionic bond) to form a stable arrangement. In order to get a stable arrangement must be fulfilled the octet rule. This establishes that an atom could share (covalent bond) win or lose (ionic bond) electrons with other atoms till every atom has eight valence electrons. The complete outer shell of valence electrons make elements stable to get a stable noble gas configuration.
It’s the third one because Cl has 17 protons bc of the numeric number and 18 electrons bc it’s always the opposite and 18 neutrons because you subtract 35-17=18
