Ch 8.2 Ionic Bond Properties

Ionic Bonds Ions – Atom or group of atoms that has become electrically chargedIons – Atom or group of atoms that has become electrically charged Negative ion (-) – gains extra electronNegative ion (-) – gains extra electron Positive ion (+) – loses an electronPositive ion (+) – loses an electron Forming IONs depends upon Valence ElectronsForming IONs depends upon Valence Electrons –Sodium has ONE Valence Electron (wants to give one away to have full electron shell) –Chlorine has SEVEN Valence Electrons (wants to TAKE one electron to have full electron shell)

Ionic Bonds IONIC Bond is formed by the ATTRACTION between 2 oppositely charged ionsIONIC Bond is formed by the ATTRACTION between 2 oppositely charged ions IONIC Bonds are caused by DONATING ElectronsIONIC Bonds are caused by DONATING Electrons –Ions are electrically charged –Ionic compounds are electrically neutral

IONIC Bonds

Ionic Bonds The number of electrons lost by the Cation MUST EQUAL the number of electrons gained by the Anion.The number of electrons lost by the Cation MUST EQUAL the number of electrons gained by the Anion. –Calcium makes a 2+ cation –Fluorine makes a 1- anion –Therefore it takes 2 fluorine atoms to combine with one calcium atom to create calcium fluoride –Chemical formula is CaF 2

IONIC Bonds Polyatomic Ions – an ion made of more than one atomPolyatomic Ions – an ion made of more than one atom –CO 3 (Carbonate) –SO 4 (Sulfate) Naming Ionic CompoundsNaming Ionic Compounds –Name of positive ion comes first –Name of negative ion comes second, plus – ide –Example: NaCl = sodium chloride, –Example: KI = potassium iodide

Properties of Ionic Compounds Crystal shapeCrystal shape –Alternate positive and negative ions in patterns –Crystals are all the same shape for each compound High melting pointsHigh melting points –Table Salt Melting point is 801 o C Conduct electricityConduct electricity –Dissolve in water –Ions become more loosely associated –Pass electrical charges along

2.3 Review Questions 1.How does an Ion form from an atom? –The atom gains or loses an electron 2.What properties may be used to identify an ionic compound? –Crystal shape, high melting point, conducts electricity 3.Why are ions in an ionic compound attracted to each other? –They are oppositely charged

2.3 Review Questions 4.Name these compounds: NaF, BeI 2, K 2 SO 4, CaO, H 2 S, MgCO 3 –Sodium fluoride –Berylium Iodide –Potassium Sulfate –Calcium Oxide –Hydrogen Sulfide –Magnesium Carbonate

2.3 Review Questions 5.Solid Salt does not conduct electricity. How then does dissolving salt in water allow electricity to flow? Water breaks the ions apart, allowing the ions to move freely.Water breaks the ions apart, allowing the ions to move freely. 6.The metal Scandium has 3 valence electrons. What is the formula for the ionic compound formed from Scandium and Iodine? –ScI 3 –Scandium has 3 valence electrons to donate, but each Iodine can only take one. Therefore, it takes 3 iodines to bond with one Scandium.

Ionic Compounds Lab #1 Substances Tested: benzoic acid, (C6H5COOH)benzoic acid, (C6H5COOH) magnesium chloride, (MgCl2)magnesium chloride, (MgCl2) petrolatum (vaseline)petrolatum (vaseline) potassium iodide (KI) replaced with potassium BROMIDE (KBr)potassium iodide (KI) replaced with potassium BROMIDE (KBr) sodium sulfate (Na2SO4)sodium sulfate (Na2SO4) sucrose (C12H22O11)sucrose (C12H22O11) sodium bicarbonate (NaHCO3)sodium bicarbonate (NaHCO3) Unknown #1Unknown #1 Unknown #2Unknown #2 What do you observe about the unknown? Is it ionic or not?Is it ionic or not? What do you think it might be good for?What do you think it might be good for? What do you think it is?What do you think it is? How could you test it further to find out?How could you test it further to find out?