# If we have an atom for which Z=17 that possesses "16 electrons", how would we represent it symbolically?

If $Z$, the atomic number, $=$ $17$, the element MUST be chlorine.
The atomic number relates to the number of protons, fundamental positively charged particles in the nucleus. The number of protons defines the element. Because there are $16$ electrons only (negatively charged particles which orbit the nucleus), we would represent the element as $C {l}^{+}$, which is an unusual situation for this element to be in (normally it forms the $C {l}^{-}$ ion!). There are 6 valence electrons on this species.
Do you have to remember this? No, because you should always be given a copy of the Periodic Table. You should have access to one now, and you certainly should be able to tell me what element we have when $Z$ $=$ $16$, and $Z$ $=$ $18$.