Chlorine must obtain an electron from another atom to become negative.
Answer: gain one electron
Explanation:
Chlorine is an element with atomic number 17 and thus contain 17 electrons. It is a p block element as the last electron enters the p orbital.
The electrons are filled according to Afbau's rule in order of increasing energies and thus the electronic configuration of chlorine is:
[tex][Cl]=1s^22s^22p^63s^23p^5[/tex]
Chlorine atom will gain one electron to gain noble gas configuration and form chloride ion with -1 charge.
[tex][Cl^-]=1s^22s^22p^63s^23p^6[/tex]
