How many valence electrons does chlorine (cl) have?
view the periodic table.
a. 4
b. 6
c. 7

B. 7

The electron configuration of Chlorine is 2-8-7
The valence shell is the outermost shell or the last number = 7 electrons

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts