# Chapter 2 - Atoms, Molecules, and Ions - Exercises: 70

a) 13 - Aluminum - ion - $Al^{3+}$ b) 34 - Selenium - ion - $Se^{2-}$ c) 56 - Barium - ion - $Ba^{2+}$ d) 7 - Nitrogen - ion - $N^{3-}$ e) 87 - Francium - ion - $Fr^{+}$ f) 35 - Bromine - ion - $Br^{-}$

#### Work Step by Step

Note - All elements either lose or gain electrons to have a total of eight electrons in their valence/last shell to become stable. a) Aluminum - Lies in group 13, where all elements have three valance electrons, and thus lose 3 electrons to acquire net positive charge (3+) b) Selenium - Lies in group 16, where all elements have six valance electrons, and thus gain 2 electrons to acquire net negative charge (2-) c) Barium - Lies in group 2 , where all elements have two valance electrons, and thus lose 2 electrons to acquire net positive charge (2+) d) Nitrogen - Lies in group 15, where all elements have five valance electrons, and thus gain 3 electrons to acquire net negative charge (3-) e) Francium - Lies in group 1 , where all elements have one valance electron, and thus lose 1 electrons to acquire net positive charge (1+) f) Bromine - Lies in group 17 (Halogens), where all elements have seven valance electrons, and thus gain 1 electrons to acquire net negative charge (1-)

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