Ionic Bonding Science 10

Ionic BondingScience 10

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Keeping Track of Electrons• The electrons responsible for the chemical

properties of atoms are those in the outer energy level.

• Valence electrons – The electrons in the outer energy level (in valence shell).

• Kernel (core) electrons -those in the energy levels below the valence shell.

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Keeping Track of Electrons

• Atoms in the same column• Have the same number of outer electrons

(valence electrons).• Easily found by looking up the group number on

the periodic table.• Group 2 - Be, Mg, Ca, .- 2 valence electrons• The last digit in the representative group

number gives the number of valence electrons

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Electron Dot diagrams (Lewis Structure)

• A way of keeping track of valence electrons.

• How to write them• Write the symbol.• Put one dot for each valence

electron• Don’t pair up until they have

to

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The Electron Dot diagram for Nitrogen

Nitrogen has 5 valence electrons.

First we write the symbol.

NThen add 1 electron at a time to each side.Until they are forced to pair up.

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Write the electron dot diagram for

• Na• Mg• C• O• F• Ne• He

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Electron Configurations for Cations

• Metals lose electrons to attain noble gas configuration (Born losers).

• They make cations (positive ions).• If we look at electron configuration it

makes sense.• Na 2, 8, 1 - 1 valence electron• Na+ 2, 8 -noble gas configuration (Ne)

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Electron Dots For Cations• Metals will have very few valence electrons

CaCalcium has two valence electrons (Group 2)

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Electron Dots For Cations• Metals will have very few valence electrons• These will come off

Ca9

Electron Dots For Cations• Metals will have very few valence electrons• These will come off• Forming cations (positive ions)

Ca2+

Calcium has lost two valence electrons10

Electron Configurations for Anions

• Nonmetals gain electrons to attain noble gas configuration.

• They make anions (negative ions).• If we look at electron configuration it makes

sense.• S 2, 8, 6 - 6 valence electrons• S2- 2, 8, 8 -noble gas configuration (Ar).

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Electron Dots For Anions• Nonmetals will have many valence electrons.• They will gain electrons to fill outer shell.

P P3-

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Stable Electron Configurations• All atoms react to achieve noble gas

configuration.• Noble gases have 8 valence electrons .• Also called the octet rule.

Ar13

Ionic Bonding - the basics• Metals form positive ions.• Non-metals form negative ions.• Anions and cations are held together by opposite

charges.• Ionic compounds are called salts.• The bond is formed through the transfer of electrons.

(From metals to nonmetals.)• Electrons are transferred to achieve noble gas

configuration.• The valence electrons determine the formula. (Simplest

ratio is called the formula unit.)

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Ionic Bonding

Na Cl

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Ionic Bonding

Na+ Cl-

Na lost 1 electron to form 1+ cation Cl gains 1 electron to form a 1- anionThe + and – attract (force of attraction is called an ionic bond) holds the ions together.The ratio is 1:1 so the formula is NaCl

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Counting ElectronsDuring the formation of an ionic compound the total

number of electrons lost (by metals in forming cations) must equal the total number of electrons gained (by non-metals in forming anions).

Ca Group 2 loses 2 e-

P Group 15 (5A) gains 3e-

To keep totals equal a LCM of 6 is used.Therefore: 3 x Ca = 3 x 2+ = 6+

2 x P = 2 x 3- = 6-

6 lost (+6) = 6 gained (6-) Charges cancel.

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Ionic Bonding

• All the electrons must be accounted for, total lost = total gained!

Ca P

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Ionic Bonding

Ca P

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Ionic Bonding

Ca2+ P

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Ionic Bonding

Ca2+ P

Ca21

Ionic Bonding

Ca2+ P3-

Ca22

Ionic Bonding

Ca2+ P3-

Ca P23

Ionic Bonding

Ca2+ P3-

Ca2+ P24

Ionic Bonding

Ca2+ P3-

Ca2+ P

Ca

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Ionic Bonding

Ca2+ P3-

Ca2+ P

Ca

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Ionic Bonding

Ca2+ P3-

Ca2+P3-

Ca2+

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Ionic Bonding

Ca3P2

Formula UnitThe Ca to P ratio is 3:2 so:

3 x 2+ = 6+ 2 x 3 – = 6 –6+ + 6– = 0

(# e– lost = # e– gained)

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+1 +2 +3 +4 -3 -2 -1 0

Most Transition Metals do not have form cations of one fixed charge, they tend to have variable charges.

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Properties of Ionic compounds:• High melting points.• Conduct electricity when dissolved in water or in

molten state. • They do not conduct electricity in solid state because

the electrons are not able to move.• Ionic substances tend to be electrolytes - a substance

that dissolves in water to produce a solution that will conduct electricity.

• Solid are a crystal lattice.

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Some common binary ionic compounds:

• NaCl – table salt• KCl – potash• AlCl3 antiperspirant

• CaCl2 – road salt

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Naming fixed binary ionic compounds

• Ionic compounds are formed between metals and non-metals. When naming them, we name the Cation (metal) first, then we name the anion (non-metal) last- changing the last part of the name of the element to “ide”.

• Ex: chlorine – chloride• oxygen – oxide• nitrogen - nitride

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Formula Writing and Naming:Fixed Binary ionic compounds

• Formula: write the cation first and anion last.• Name: Name the cation first (use the element name) • Name the anion but change the ending to “ide”

So, Formula: KClName: potassium chloride

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Example- Show the formation of the compound formed between Na and O.

Formula Na2O

Name: sodium oxide34

Show the formation of CaCl2.

Name: calcium chloride

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• Show the formation of the following fixed binary ionic compounds using electron-dot structures (Lewis structures). Also write the names of the compounds.

• a) K3P• b) NaF• c) Al2O3

• Predict the formula and name the compounds formed when the following elements react.

• a) K and F• b) Li and O• c) Mg and P

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Write the formula and the name for the ionic compound formed from each of the following ions.

• a) Ca2+ and Cl-

• b) Al3+ and N3-

• c) Be2+ and O2-

• d) Be2+ and N3-

• e) K + and S2-

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Practice: Name the following binary ionic compounds:

A) MgOB) Al2SC) K3ND) ZnF2

E) CaCl2F) LiClG) CsFH) NaBrI) BaF2

J) HCl

Magnesium oxideAluminum sulfidePotassium nitridezinc fluoridecalcium chlorideLithium chlorideCesium fluorideSodium bromideBarium bromideHydrogen chloride

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What about those ones in the “middle”?

• Metals, so they form positive ions (cations)• They can form different ions (variable charge)

eg, Fe2+, Fe3+

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Examples….

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Naming variable binary ionic compounds

• Ionic compounds formed between metals with variable charge and non-metals. When naming them, we name the metal first and state the charge in Roman numerals in brackets , then we name the non-metal last- changing the last part of the name of the element to “ide”.

• Roman numerals:• 1 – I 4 – IV 7 – VII 10 – X • 2 – II 5 – V 8 – VIII • 3 – III 6 – VI 9 – IX

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Ionic compounds with transition metals:

FeCl3 Fe3+ 3Cl1-

Cl Fe Cl

FeCl3

Cl

iron(III) chloride

Cu2SCu S Cu 2Cu1+ S2-

copper(I) sulfide

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Write the formulas for the following compounds.a) copper(I) oxideb) lead(IV) bromidec) iron(III) sulfided) nickel(III) fluoridee) manganese(IV) sulfideWrite the names of the following compounds.(Use the

anion to calculate the charge of the cation.)a) FeCl2

b) FeOc) Cu2O

d) PbO243

Polyatomic ions…ions made up of 2 or more elements.

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Ionic compounds with polyatomic ions…

NH41+ and S2-

NH4 1+ S 2- NH4

1+ Charges cancel

2NH41+ S2-

(NH4)2S

ammonium sulfide45

Write the formula for the following ionic compounds

a) Ca2+ & NO31-

b) Na1+ & OH1-

c) K1+ & SO42-

d) Ba2+ & PO43-

e) Li1+ & HCO31-

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Naming Ionic Compounds with polyatomic ions

Name the cation: 1) fixed name the element 2) variable element name followed by (roman numeral) 3) name the positive polyatomic (only for NH4

1+) then the anion

Name the negative polyatomic ionWrite the name for the ionic compounds from the previous

slide.

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