Ch. 7 Ionic Bonding

Ch. 7 Ionic BondingChemistry Homeworkp. 193 #3-11, p. 207 - 208 # 31-32, 35-40, 55-56, 58-59, 62-63, 65 DUE WEDNESDAY p. 199 # 16, 18-20, p. 207-208 # 42,45 DUE THURSDAYQuiz over Table 7.2 on Wends, Nov 9Test over Ch. 7 on Tuesday, Nov. 15 (tentative)Review 1. What is an ion? ion an atom with a positive or negative charge (an electron has been lost or gained)2. Where on the periodic table are the metals located? Nonmetals?

Valence ElectronsCore Electrons inner electrons, do not participate in bondingValence Electrons outer electrons, electrons in the highest occupied energy levelnumber of valence electrons largely determines the chemical properties of an elementSo which electrons in an electron configuration are core and valence?

Be [He] 2s2P [Ne] 3s2 3p3 CoreValenceCoreValenceSo how do I find this valence number?The valence electrons an atom has is the same as its group number for a representative (main group) element

So how do I find this valence number?So how many valence electrons would Na have?1Iodine?7Krypton?8

How do I keep track of all these valence electrons?Valence electrons are VERY important for chemistry and reactions!Why? Chemists have electron dot structures diagrams that show valence electrons as dots

How do I keep track of all these valence electrons?What do you notice about valence electrons down a group?Electron configuration remains the same down a group, only the core electrons change

PracticeHow many valence electrons does Al have? Draw the Lewis dot structure.Electron configuration:Valence Electrons: Lewis dot structure:

[Ne] 3s2 3s1 3 Crystal StructuresIn crystalline materials, elements repeat in repetition to give a 3D arrangement known as a crystal latticeA unit cell is the smallest part of the lattice that represents the entire lattice (repeated part)4 types of unit cells:PrimitiveBody-centeredFace-centeredHexagonal close-packedCrystal Structures

Primitive body-centered

Hexagonal close-packed face-centeredPart I: MetalsCrystal coordination number (CN): number of neighbors to an atom in a unit cellExample: simple cubic is 6

Part I: MetalsCrystal coordination number (CN): number of neighbors to an atom in a unit cellFace-centered:12Body-Centered:8Hexagonal:12Lets Think!We know noble gases are very stable. How can we get the other elements to become stable like the noble gases?Hint: Think of valence electrons!

Octet RuleAll elements want eight valence electrons (except H and He)Why?Achieve noble gas configuration, most STABLE2 electrons come from the s subshell and 6 from the p subshellWhy can H and He NOT have eight valence electrons (Hint: they are considered stable with TWO valence electrons)No p subshell!Octet RuleElements will tend to gain or lose enough electrons to fulfill their octetWill metallic elements gain or lose electrons? Lose, much easier to lose electrons than gain electronsWill nonmetallic elements gains or lose electrons?Gain, much easier to gain electrons (can also share electrons)Octet RuleMetallic elements lose electronsWhy?In simple termseasier to lose than to gain to form the octetNonmetallic elements gain electronsWhy?In simple terms, easier to gain a few electrons than lose themNow lets consider periodic trends!Nuclear attraction across:Shielding effect across:Kinetic energy across:This means:

Increases across, nonmetals held tighter than metalsRemains constant, does not offset nuclear attractionRemains constantMetals hold onto their electrons less tightly so it is easier for metals to lose their electrons. Additionally, nonmetals hold onto their electrons tighter . This trend, and the fact that nonmetals have higher electron affinity, means nonmetals tend to gain electrons.Octet RuleIf metals lose electrons, they will form ions. Will these ions be negatively or positively charged?If nonmetals gain electrons, will their ions be negatively or positively charged?

Octet RuleIons get special names to distinguish between those ions that are positively charged and those that are negatively chargedCation positively charged ionLets try sodium!Electron configuration:Original electron dot diagram:How many electrons will it lose?New electron dot diagram:New electron configuration

[Ne] 3s1[Ne] 1

Na+Octet RuleIons get special names to distinguish between those ions that are positively charged and those that are negatively chargedCation positively charged ion

Octet Rule - CationsIons get special names to distinguish between those ions that are positively charged and those that are negatively chargedCation positively charged ion

I wonderMg has the electron configuration of [Ne] 3s2. How many electrons would it lose or gain stability?2Will it take more or less energy to remove the second electron than the first electron?Lets use electron dot structures to show its loss of 2e-

Octet Rule - CationsWe just did one example of formation of a cation from Group 1 and Group 2. What can we say about the general formation of cations from Group 1 and the general fromation of cations from Group 2?Group 1 form +1 cationGroup 2 form + 2 cation

What about those transition metals?Its extremely hard for transition metals to lose enough electrons to form a noble gas configuration. Why?They would have to lose all the s and d electrons!The transition metals ending with ns1(n-1)d10 can lose that 1s electron to achieve pseudo noble-gas electron configurationWhat is one element that does this?Elements with the configuration ns1(n-1)d5 can also lose that 1s electron to achieve half shell stabilityWhat is one element that can do this?What about those transition metals?

Octet Rule - AnionsIons get special names to distinguish between those ions that are positively charged and those that are negatively chargedAnion negatively charged ionLets try chlorine!Electron configuration:Electron diagram:How many electrons will it gain? New electron diagram:New electron configuration

[Ne]3s2 3p5[Ne]3s2 3p61

Cl-Octet Rule - AnionsIons get special names to distinguish between those ions that are positively charged and those that are negatively chargedAnion negatively charged ion

Octet Rule - AnionsIons get special names to distinguish between those ions that are positively charged and those that are negatively chargedAnion negatively charged ion

I wonderO has the electron configuration of [He] 2s2 2p4. How many electrons would it gain to gain stability?2Will it take more or less energy to gain the second electron than the first electron?Lets use electron dot structures to show its gain of 2e-

Octet Rule - AnionsHow many electrons need to be gained by each group in group 5,6, and 7 to be stable?

Octet Rule

Common IonsEveryone loves memorizing stuff in chemistry! Lets memorize some more!(Trust me, itll make your life 10x easier if you just memorize them now and get it over with!)

Common Ions

Lets Think!We all know that certain elements will bond together to form molecules, such as NaCl (table salt). Why is this?Hint: Think of valence electrons.

Ionic BondingIonic compound composed of metal cations and nonmetal anionsThey are still electrically neutralWhy?The charges of the cation and anion cancel outThe negatively charged anion and the positively charged cation attract each other by electrostatic forces (force holding a cation and anion together due to their charge)Ionic BondingIonic compound composed of metal cations and nonmetal anionsLets go back to the formation of NaClWhats the electron configuration of Na?Of Cl?Their valence electrons can add together to form an ionic compoundnow both elements are happyjust like Justin and Selena![Ne] 3s1[Ne] 3s2 3p5

Ionic BondingIonic compound composed of metal cations and nonmetal anions

Ionic BondingIonic compound composed of metal cations and nonmetal anions

Ionic BondingIonic compound composed of metal cations and nonmetal anions

Ionic BondingSo Na+ and Cl- combine to form NaClNaCl is the chemical formula or a way to show the kinds and numbers of atoms in the smallest unit of a substanceSo there is 1 Na+ for every 1 Cl-What would Mg+2 and Cl-1 form?There is 1 Mg+2 for every 2 Cl-1 so MgCl2Think of it this way: the charges have to become neutralIonic BondingThe charges must become neutral

What about Sr+2 and F-?SrF2

Ionic BondingAnother way to do it is balance out the chargesEx: 1 Mg has a +2 charge and 1 O has a -2 charge. The charges are already balanced!So we have.MgOWhat about.1 Be has a +2 charge and 1 Br has a -1 charge. How many Br will be needed to balance out the charges?2so that gives us.BeBr2