Answer
Atom | Gain (G) or Lose (L) Electrons | Ion Formed
--- | --- | ---
K | L |K+
Cs | L | Cs+
Br | G | Br-
S | G | S2
Se | G | Se2-
Work Step by Step
K (Potassium): Potassium is a Group 1 (alkali metal) element, which means it has a single valence electron. To achieve a stable electron configuration, potassium will lose this valence electron, forming the K+ cation.
Cs (Cesium): Cesium is also a Group 1 (alkali metal) element, and it will lose its single valence electron to form the Cs+ cation.
Br (Bromine): Bromine is a Group 17 (halogen) element, which means it has seven valence electrons. To achieve a stable electron configuration, bromine will gain one electron, forming the Br- anion.
S (Sulfur): Sulfur is a Group 16 (chalcogen) element, which means it has six valence electrons. To achieve a stable electron configuration, sulfur will gain two electrons, forming the S2- anion.
Se (Selenium): Selenium is also a Group 16 (chalcogen) element, and it will gain two electrons to form the Se2- anion.
