Presentation on theme: "Ionic Bonds For review pages Sections 8:1- 8:3"— Presentation transcript:
1Ionic Bonds For review pages 211-227 Sections 8:1- 8:3 Forming Chemical BondsThe Formation and Nature of Ionic BondsNames and Formulas for Ionic Compounds
2Valence Electrons What are valence electrons Valence electrons are the outermost electrons that are available for bondingThe number of valence electrons will determine how many bonds the atom can form.What kind of elements form bondsAtoms that have unfilled valence shells are considered unstable. Atoms will try to fill their outer shells by bonding with other atoms.
3How does an atom become a positive ion? When an atom loses an electron it becomes a positive ion called a cation. When a cation loses outermost valence electron(s):Ionic radius is smaller than the atomic radius.Achieves a stable octet like_________Example:Sodium (Na) has 11 + and 11 - charges as a neutral atom. When it loses an electron it has 11 + and 10 - charges or a net charge of +1. When sodium cations look in the mirror they see _________.
4When anions gains an outer most valence electron: How does an atom become a negative ion?When an atom gains an electron it becomes a negatively charged ion called an anion.When anions gains an outer most valence electron:Ionic radius is larger than the atomic radius.Achieves a stable octet like_________Example: Chlorine has 17 + and 17 - charges. When it gains an electron, it have 17 + and 18 - for a net charge of -1. When a chloride ion looks in the mirror it sees ___
5Atomic vs Ionic Radii Cations like Lithium get smaller Anions like Fluoride get bigger
6How do ions form neutral compounds? Positive and negative ions combine their charges which cancel out to form a neutral compound.Example:Na Cl -1 becomes NaCl with a zero net charge
7When do ionic bonds form between metals and non-metals.between oppositely charged atoms (ions).by the transfer of electrons (exchanging).One atom (cation) donates electrons to the high electronegativity element (anion)One atom (anion) take electrons from low ionization energy elements (cations)
8Ionic compounds form crystals Ionic bond between ions form crystals that are regular repeating structures called lattices.In an ionic bond, oppositely charged ions are strongly held together by electrostatic forces.
9What characteristics do ionic compounds share? A crystal structure when solid (lattice)A high melting point -many strong bonds to overcome between the ionsA high boiling point -many strong bonds to overcome between the ionsA tendency to form ions in solutionAre conductors of electricity in solution or when meltedBut nonconductors as solids
10How does electrical conductivity of ionic compounds change when they are melted or dissolved in water?Ionic Compounds tend to conduct electricity because their ions separate in water allowing for the transfer of electrons through the solution.Electrical conductivity is the ability of a material to carry the flow of an electric current (a flow of electrons).
11How many potassium ions are needed to balance the charge of one sulfide ion? Potassium has a charge of +1.Sulfide has a charge of -2.It takes two potassium ions to neutralize one sulfide ion.K2S = Potassium sulfide
12Predict the formulas for calcium chloride and potassium phosphate? AnswersCaCl2K3PO4
13What are polyatomic ions? NH4+ ammoniumPO4-3 phosphateBecause they are composed of two or more different elements covalently bonded.
14Drawing Ionic BondsWe can illustrate ionic bonding using Lewis structures.1 – Draw the Lewis structure for each element.Ex: Na Cl2 – Draw arrows to show the gain/loss of electrons
15Lewis Dot Formula continued 3 – Draw ion Lewis diagrams showing the new charge for each ion.Ex:The chemical formula for the compound formed represents the ratio of negative ions to positive ions.Ex: NaCl – for every 1 sodium ion, there is also 1 chlorine ion.
16Practice Drawing Ionic Bonds Elements Lewis Ion Lewis FormulaDiagram DiagramCalciumFluorineMagnesiumBromine
17Where do ions come from? Ions can form in a solution. Ionic bonds can form between a metal ion and a nonmetal ion or nonmetallic polyatomic ionUsually from the breaking apart of the ions of a salt formed by an acid-base reaction or a metal and acid reaction.
18Ionic Compounds Form when reacting with an acid Hydrogen will bond covalently with a nonmetal such as chlorine to form hydrochloric acid- HCl.A metal will react with an acid to release hydrogen and form a metallic salt.Zn + 2 HCl ZnCl2 + H2
19Okay, so is that all?An acid will also react with a hydroxide compound of a metallic ion and hydroxide (OH) ion to form an ionic compound and water.3NaOH + H3PO4 Na3PO4 + H2OSodium hydroxide and phosphoric acid become sodium phosphate and water
20Okay, so is that all?A nonmetallic ion such as ammonium can also form an ionic compound.NH4OH + HCl NH4Cl + H2Oammonium hydroxide and hydrochloric acidbecome ammonium chloride and water
21Ionic Compound Formulas The subscript indicates the number of ions of an element in a molecule of a compound.Na3PO Na ion and 1 PO4 ionCa3(PO4)2 3 Ca ions and 2 PO4 ionsNote the parens around the polyatomic ion when a subscript is needed.
22Naming Ionic Compounds The first name of the ionic compound is the name of the positive ion. The second name is the name of the negative ion.positive ion negative ionFor example:Magnesium sulfideAmmonium chloridePotassium oxide
23Vocabulary Ion- a charged atom Cation- a positively charged ion (lost electron)Anion- negatively charged ion (gained electron)Ionic bond- forms when electrons are lost or gained between ionsIons in a crystal are arranged in a lattice.