Final answer:
An atom with a -1 charge and 17 protons has 18 electrons and a mass number of 35. It is an isotope of chlorine and likely to bond with alkali metals like sodium to form stable compounds.
Step-by-step explanation:
If an atom has a -1 charge, 17 protons, and 18 neutrons, the atom will have 18 electrons. This is because the negative charge indicates that there is an additional electron compared to the number of protons. The number of protons minus the negative charge (17 - (-1)) equals the number of electrons, which is 18. The mass of the atom is determined by adding the number of protons to the number of neutrons, which equals 35 (17 protons + 18 neutrons = 35). This atom is an isotope of chlorine, which is likely to bond with elements that require one additional electron to achieve electron configuration stability, such as sodium or other alkali metals, to form salts like sodium chloride.