Answer
a) $Xe$; b) $Rb$; c) $Ar$; d) $At$
Work Step by Step
a. The element that is a member of the same family as oxygen and whose most stable ion contains 54 electrons is Xenon (Xe). Xenon belongs to the same group as oxygen on the periodic table, Group 18 (Noble Gases), and its most stable ion is Xe2+ with 54 electrons.
b. The element that is a member of the alkali metal family and whose most stable ion contains 36 electrons is Rubidium (Rb). Rubidium is an alkali metal in Group 1 of the periodic table, and its most stable ion is Rb1+ with 36 electrons.
c. The noble gas with 18 protons in the nucleus is Argon (Ar). Argon is a noble gas in Group 18 of the periodic table, and it has 18 protons in its nucleus.
d. The halogen with 85 protons and 85 electrons is Astatine (At). Astatine is a halogen in Group 17 of the periodic table, and it has 85 protons and 85 electrons.
