Ions Ion Charged atom of an element Formed

Ions

Ion • Charged atom of an element – Formed from gaining or losing electrons – Charge of ion = oxidation number

Anion • Formed from an element gaining electrons • Negatively charged • Usually nonmetals form anions

Cation • Formed from losing electrons • Positively charged • Usually metals form cations

Why do elements form ions? • Elements want to be like noble gases – full set of valence electrons = 8 – Stable – Unreactive

How many electrons will each need to gain or lose to become an ion?

How many electrons will each need to gain or lose to become an ion? Na Mg

Elements and Oxidation Numbers • Elements in the same group (Main group elements 1 -2 and 13 -18) have the same oxidation numbers – Group 1 = +1 – Group 2 = +2 – Group 13 = +3 – Group 14 = +4 or -4 – Group 15 = -3 – Group 16 = -2 – Group 17 = -1 – Group 18 = 0

Ion Lewis Dot Diagrams • Always: • Add bracket around element symbol • Add charge as superscript on right side If loses electrons, no valence electrons shown around symbol If gains electrons, there should be 8 valence electrons shown (except for H)

Practice Question 1 Which of the following elements are cations as ions? Na , P , O , Cl, Mg , K , H

Practice Question 2 What is the charge of Aluminum as an ion and how many electrons will it have?

Practice Question 3 Draw the lewis dot diagram for the element Oxygen and the ion Oxygen.

Practice Question 4 What group on the periodic table will have a charge of +3?