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IB Topic 4: Bonding4.1: Ionic bonding

Essential Idea: Ionic compounds consist of ions held together in lattice structures by ionic bonds.

Nature of Science:Use theories to explain natural phenomena –

molten ionic compounds conduct electricity but solid ionic compounds do not. The solubility and melting points of ionic compounds can be used to explain observations. (2.2)

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IB Topic 4: Bonding4.1: Ionic bonding

Understandings:1. Positive ions (cations) form by metals losing

valence electrons2. Negative ions (anions) form by non-metals

gaining electrons.3. The number of electrons lost or gained is

determined by the electron configuration of the atom.

4. The ionic bond is due to electrostatic attraction between oppositely charged ions.

5. Under normal conditions, ionic compounds are usually solids with lattice structures.

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IB Topic 4: Bonding4.1: Ionic bonding

Applications and Skills:1. Deduction of the formula and name of an ionic

compound from its component ions, including polyatomic ions.

2. Explanation of the physical properties of ionic compounds (volatility, electrical conductivity, and solubility) in terms of their structure.

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IB Topic 4: Bonding

Only one group of elements are stable (nonreactive). Which group?

Nobel GasesWhat is unique about their electron structure?

Filled outer s & p orbitals, 8 electrons

All other elements react in order to achieve this stable electron configuration.

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IB Topic 4: Bonding

Ionic Bond: Transfer of electrons from metal to non-metal; metal + non-metal

Covalent Bond: Sharing of electrons between non-metals; nonmetal + nonmetal

U1. Positive Ions

Positive Ions (cations): metals that lose e-Group 1• Lose 1 valence electron• Charge of +1: Li+, Na+, K+

Group 2• Lose 2 valence electrons• Charge of +2: Mg2+, Ca2+

Group 13• Lose 3 valence electrons• Charge of +3: Al3+

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U2. Negative Ions

Negative Ions (anions): non-metals that gain e-Group 15• Gain 3 electrons • Charge of -3: N3-, P3-

Group 16• Gain 2 electrons • Charge of -2: O2-, S2-

Group 17• Gain 1 electron • Charge of -1: F-, Cl-, Br-, I-

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U3. Electron Configuration and Ion formation

Let’s look at the reaction between sodium and chlorine

What is the electron configuration for sodium?

What is the electron configuration for chlorine?

What do you think they want to do with their electrons?

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U3. Electron Configuration and Ion formation

Sodium configuration: [Ne]3s1

•If Na loses one electron then it would end in [He]2s2 2p6 and be stable.

•Then sodium has 11 protons (11+), but only 10 electrons (10-) so it acquires a charge of 1+ and becomes the sodium ion, Na+.

•In order for it to lose an electron, something has to gain an electron

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U3. Electron Configuration and Ion Formation

•Chlorine configuration: [Ne]3s2 3p5

If Cl gains one electron then it would end in [Ne]3s2 3p6 and be stable.

•Then chlorine has 17 protons (17+), and 18 electrons (18-) so it acquires a charge of 1- and becomes the chloride ion, Cl-.

•It will gain the electron from the sodium.

U1 & U2. Ion formation

Ions are formed when one or more electrons are transferred from one atom to another.

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U1 & U2. Ion formation

Na transfers 1 e- to ClNa becomes Na +1, positive ion (cation)Cl becomes Cl-1, negative ion (anion)

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U4. Ionic bond

Ionic bond is formed due to the attraction between oppositely charge ions

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U4. Ionic Bond

Reaction between Sodium and Chlorine

• Since opposite charges attract, the Na+ and Cl- ions form an ionic bond.

• ETD: Na Cl

• LDD: [Na]+ [ Cl ]-

• Formula: NaCl

• Name: Sodium chloride

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U3. Electron Configuration and Ion Formation

Reaction between Magnesium and Chlorine• Magnesium configuration: [Ne]3s2 • If Mg loses two electrons then it would end in

[He] 2s2 2p6 and be stable.

• Then magnesium has 12 protons (12+), but only 10 electrons (10-) so it acquires a charge of 2+ and becomes the magnesium ion, Mg2+.

• In order for it to lose two electrons, something has to gain two electrons

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U3. Electron Configuration and Ion Formation

Reaction between Magnesium and Chlorine• Chlorine configuration: [Ne]3s2 3p5 • If Cl gains one electron then it would end in [Ne]3s2

3p6 and be stable.

• Then chlorine has 17 protons (17+), and 18 electrons (18-) so it acquires a charge of 1- and becomes the chloride ion, Cl-.

• Since chlorine can only gain one electron and magnesium gives up two electrons, magnesium requires two chlorine atoms.

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U4. Ionic Bond

Reaction between Magnesium and Chlorine

• Since opposite charges attract, the Mg2+ and the 2 Cl- ions form an ionic bond.

• ETD: Mg Cl Cl

• LDD: [Mg]2+ [ Cl ]2-

• Formula: MgCl2

• Name: Magnesium chloride

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U4. Ionic Bond

Reaction between Potassium and Oxygen

Potassium configuration: [Ar] 4s1

• Potassium will lose 1 electron and become the potassium ion K+. [Ne] 3s2 3p6

• Oxygen configuration: [He]2s2 2p4

• Oxygen will gain 2 electrons and become the oxide ion O2-. [He]2s2 2p6

Two potassium atoms are needed to combine with one oxygen.

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U4. Ionic Bond

Reaction between Potassium and Oxygen

ETD: K O K

LDD:[K]2+1 [ O ]-2

Formula: K2O

Name: Potassium oxide

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Reaction between Aluminum and Bromine

Diagram the bonding between Al and Br using electron configuration, write the formula, and

give the name.

U4. Ionic Bond

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Reaction between Aluminum and BromineETD:LDD:Formula: AlBr3

Name: Aluminum bromide

U4. Ionic Bond

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Transition Metals

In most transition elements, inner electrons can become involved in the reaction

Iron can lose 2 electrons (Fe2+) or 3 electrons (Fe3+)• The name of the Fe2+ ion is iron (II) or ferrous• The name of the Fe3+ ion is iron (III) or ferric

Chromium can lose 2 electrons (Cr2+) or 3 electrons (Cr3+)• The name of the Cr2+ ion is chromium (II) or chromous• The name of the Cr3+ ion is chromium (III) or chromic

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Summary of Ionic Bonds• Formed between a metal ion and a non-metal ion

– Metal transfers valence electrons to the non-metal

• Ions are formed when atoms transfer electrons.– Cations = electron removed, + charge– Anions = electron added, - charge

• The number of electrons that are transferred is determined by the valence electrons for each atom (dots)

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Polyatomic ions are ions consisting of two or more atoms bonded together

Nitrate NO3-

Hydroxide OH-

Sulfate SO42-

Carbonate CO32-

Phosphate PO43-

Ammonium NH4+

Hydrogen carbonate (bicarbonate) HCO3-

More on chart of ions: nitrite, sulfite, perchlorate, chlorate, chlorite, hypochlorite, silicate

A&S 1: Polyatomic Ions

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MUST KNOW THESE 7

Nitrate NO3-

Hydroxide OH-

Sulfate SO42-

Carbonate CO32-

Phosphate PO43-

Ammonium NH4+

Hydrogen carbonate (bicarbonate) HCO3-

Polyatomic Ion Quiz is April 8!

A&S 1: Polyatomic Ions

A & S 1. Naming Ionic CompoundsA & S 1. Naming Ionic Compounds

RULE: Cation first, then anion

•1. Monatomic cation = name of the element

•Ca2+ = calcium ion

•2. Monatomic anion = root + -ide

•Cl = chloride ion

•CaCl2 = calcium chloride

Names of Variable IonsNames of Variable Ions

Transition metals and the metals in groups 14 and 15 (except Ag, Zn, Cd, and Al) require a Roman Numeral because they can have more than one charge (form more than one ion).

FeCl3 (Fe3+) iron (III) chlorideCuCl (Cu+ ) copper (I) chlorideSnF4 (Sn4+) tin (IV) fluoridePbCl2 (Pb2+) lead (II) chloride

Fe2S3 (Fe3+)iron (III) sulfide

• Transition metal ionic compounds• indicate charge on metal with Roman numerals

FeCl2 2 Cl- -2 so Fe is +2 iron(II) chloride

FeCl3 3 Cl- -3 so Fe is +3 iron(III) chloride

Cr2S3 3 S-2 -6 so Cr is +3 (6/2) chromium(III) sulfide

Naming Ionic Compounds

Examples:

NaCl

ZnI2

Al2O3

sodium chloride

zinc iodide

aluminum oxide

Practice 1

Complete the names of the following binary compounds:

Na3N sodium ____________

KBr potassium __________

Al2O3 __________ oxide

MgS __________ __________

Practice 1

Complete the names of the following binary compounds:

Na3N sodium nitride

KBr potassium bromide

Al2O3 aluminum oxide

MgS magnesium sulfide

Practice 2

Complete the names of the following binary

compounds with variable metal ions:

FeBr2 iron (_____) bromide

CuCl copper (_____) chloride

SnO2 ___(_____ ) ______________

Fe2O3 ________________________

Hg2S ________________________

Practice 2

Complete the names of the following binary

compounds with variable metal ions:

FeBr2 Iron (II) bromide

CuCl Copper (I) chloride

SnO2 Tin(IV) oxide

Fe2O3 Iron (III) oxide

Hg2S Mercury (II) sulfide

NONO33--

nitrate ionnitrate ion

NONO22--

nitrite ionnitrite ion

Polyatomic IonsPolyatomic Ions

You can make additional polyatomic You can make additional polyatomic ions by adding a Hions by adding a H++ to the ion! to the ion!

COCO33 -2-2 is carbonate is carbonate

HCOHCO33–– is hydrogen carbonate is hydrogen carbonate

HH22POPO44–– is dihydrogen phosphate is dihydrogen phosphate

HSOHSO44–– is hydrogen sulfate is hydrogen sulfate

Polyatomic IonsPolyatomic Ions

Writing Ionic Formulas from Names

• Write each ion, cation first. Don’t show charges in the final formula.

• Overall charge must equal zero.– If charges cancel, just write symbols.– If not, use subscripts to balance charges.

• Use parentheses to show more than one of a particular polyatomic ion.

• Use Roman numerals indicate the ion’s charge when needed

Writing Ionic Formulas

Sodium SulfateNa+ and SO4 -2

Na2SO4

Iron (III) hydroxideFe+3 and OH-

Fe(OH)3

Ammonium carbonateNH4

+ and CO3 –2

(NH4)2CO3

Writing Formula Practice 1

1. aluminum nitrate

a) AlNO3 b) Al(NO)3 c) Al(NO3)3

2. copper(II) nitrate

a) CuNO3 b) Cu(NO3)2 c) Cu2(NO3)

3. Iron (III) hydroxide

a) FeOH b) Fe3OH c) Fe(OH)3

4. Tin(IV) hydroxide

a) Sn(OH)4 b) Sn(OH)2 c) Sn4(OH)

Writing Formula Practice 1

1. aluminum nitrate

a) AlNO3 b) Al(NO)3 c) Al(NO3)3

2. copper(II) nitrate

a) CuNO3 b) Cu(NO3)2 c) Cu2(NO3)

3. Iron (III) hydroxide

a) FeOH b) Fe3OH c) Fe(OH)3

4. Tin(IV) hydroxide

a) Sn(OH)4 b) Sn(OH)2 c) Sn4(OH)

Naming Polyatomic Ionic Compounds

Contains at least 3 elementsThere MUST be at least one polyatomic ion

(it helps to circle the ions)Examples:

NaNO3 Sodium nitrate

K2SO4 Potassium sulfate

Al(HCO3)3 Aluminum bicarbonate

or

Aluminum hydrogen carbonate

Naming Polyatomic Compounds Practice

Match each set with the correct name:

1. Na2CO3 a) magnesium sulfite

MgSO3 b) magnesium sulfate

MgSO4 c) sodium carbonate

2 . Ca(HCO3)2 a) calcium carbonate

CaCO3 b) calcium phosphate

Ca3(PO4)2 c) calcium bicarbonate

Naming Polyatomic Compounds Practice

Match each set with the correct name:

1. Na2CO3 a) magnesium sulfite

MgSO3 b) magnesium sulfate

MgSO4 c) sodium carbonate

2 . Ca(HCO3)2 a) calcium carbonate

CaCO3 b) calcium phosphate

Ca3(PO4)2 c) calcium bicarbonate

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U5. Lattice Structure

Ionic compounds form crystalline solids that have a lattice structure; 3D repeating units of alternating positive and negative ions

Sodium Chloride: Each sodium ion is surrounded by up to 6 chloride ions and each chloride ion is surrounded by up to 6 sodium ions.

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Melting Point: temperature at which change from a solid to a liquid

Boiling Point: temperature at which change from a liquid to a gas

Volatility - how easily it is converted to gas

Important Terms

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Conductivity- conducts electricity; depends on whether the substance contains electrically charged particles that are free to move through it

Solubility - solute’s ability to dissolve in solvent

Important Terms

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A & S 2: Ionic Bond Physical Properties

Ionic Compounds:• Solid at Room temperature• Hard and brittle due to lattice structure• Held tighter by strong electrostatic forces in 3D

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A & S 2: Ionic Bond Physical Properties

Ionic Compounds: • MP: high• BP: high • Volitility: low• Conductivity: not when solid; must be dissolved

or molten to conduct• Solubility: dissolve in polar solvents (water), do

not dissolve in non-polar solvents (hexane)

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Electronegativity DifferenceIonic bonds: electronegativity differences

greater than or equal to 1.7

• Compare the electronegativity values between 2 atoms to determine bond type

• Subtract the smaller value from the larger to determine difference

Ex: Na and N: 3.0 – 0.9= 2.1 = IONIC