compounds and their bonds ionic bonds & naming ionic compounds

Compounds and their Bonds

Ionic Bonds &

Naming Ionic Compounds

REVIEWHow do you use the Periodic Table to determine the number of valence electrons for a given element?

The group your element is in, determines the number of valence

electrons

Symbols of atoms with dots to represent the valence-shell electrons

1A 2A 3A 4A 5A 6A 7A 8A

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

REVIEW: Lewis Electron Dot Structure

A. X would be the electron dot formula for

1) Na 2) S 3) Al

B. X would be the electron dot formula for

1) B 2) N3) Cl

LEARNING CHECK

CHEMICAL BONDS:Why do atoms form bonds?

• Atoms are stable when they have 8 valence electrons• They fulfill the Octet Rule

• There is always an exception:

• Hydrogen and Helium

• Hydrogen only needs one more electron to fill its valence shell

• Helium is full with its 2 valence electrons therefore does not bond

• Atoms can fulfill the Octet Rule when they gain, lose or share electrons

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electronsC would like to

N would like toO would like to

Gain 4 electrons of lose 4 electronsGain 3 electrons

Gain 2 electrons

CHEMICAL BONDS: What types of bonds are there?

• Ionic Bonds

• Covalent Bonds

• Metallic Bonds

• Hydrogen Bonds

What is an ion?

• An ion: an atom or bonded group of atoms with a positive or negative charge

Cation: A positively charged ion

Anion: A negatively charged ion

+

-

IONIC BONDS

• Bonds formed between 2 ions by the transfer of electrons

• Result when a metal reacts with a non-metal• Metals lose electrons (transfer e- to the non-metal) to match the number of

valence electrons of their nearest noble gas

• Positive ions (CATIONS) form when the number of electrons are less than the number of protons

Group 1A metals ion 1+

Group 2A metals ion 2+

Group 3A metals ion 3+

1. Number of valence electrons in aluminum

A) 1 e- B) 2 e- C) 3 e-

2. Change in electrons for octet

A) lose 3e- B) gain 3 e- C) gain 5 e-

3. Ionic charge of aluminum

A) 3- B) 5- C) 3+

LEARNING CHECK

1. Number of valence electrons in aluminum

C) 3 e-

2. Change in electrons for octet

A) lose 3e-

3. Ionic charge of aluminum

C) 3+

SOLUTION

IONIC BONDS

• Non-metals in groups 5A, 6A, and 7A gain electrons from the metals

• Non-metals:• Accept electrons from the metal

• Gain electrons

• Negative ions (ANIONS) form when the number of electrons is more than the number of protons

Group 5A metals ion 3-

Group 6A metals ion 2-

Group 7A metals ion 1-

LEARNING CHECK

1. Number of valence electrons in Oxygen

A) 5 e- B) 6 e- C) 7 e-

2. Change in electrons for octet

A) gain 2 e- B) lose 2 e- C)gain 4 e-

3. Ionic charge for Oxygen

A) 2+ B) +4 C) 2-

SOLUTION

1. Number of valence electrons in Oxygen

B) 6 e-

2. Change in electrons for octet

A) gain 2 e-

3. Ionic charge for Oxygen

C) 2-

IONIC BONDS

• Properties• High Melting point and Boiling Point• Conductors of electricity Strong bonds; stronger than

covalent bonds• Bond by transfer electrons

REVIEW: IONIC BOND

an electron is simply transferred to another atom. By doing so, each

atom is able to have a stable valence shell. It is called an ionic bond

because the atoms become ions, a charged atom that has either lost an

electron (positive charge) or has gained an electron (negative charge).

Below is an animation of ionic bonding:

WRITING IONIC COMPOUNDS

• Write each ion, cation first

• Don’t show charges in the final formula.

• Overall charge must equal zero.

• Use parentheses to show more than one polyatomic ion.

• Stock System –

• Roman numerals indicate the ion’s charge

• used when the ion has more than one oxidation state (Transition elements)Copyright © 2009 by Pearson Education, Inc.

EXAMPLE: • Calcium Nitrate

Ca+2 NO3-1

Ca1(NO3)2

Ca (NO3)2

1(+2) + 2(-1)= 0

Cross the exponents only! not the + or -

Do NOT show 1 in the final

formulaPolyatomic

ion NO3 goes in

parentheses

This is your final formula!

Check for the overall charge to equal zero

potassium chloride

magnesium nitrate

copper(II) chloride

K+ Cl-

Mg2+ NO3-

Cu2+ Cl-

KCl

Mg(NO3)2

CuCl2

LEARNING CHECK

NAMING IONIC COMPOUNDS

• Identify the cation and anion

• Name the cation first

• Name the anion with an –ide ending

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Complete the names of the following ions: (Is it a cation or an anion?)

Ba2+ Al3+ K+

_________ __________ _________

N3 O2 F

_________ __________ _________

Learning Check

22

Ba2+ Al3+ K+

barium aluminum potassium

N3 O2 F

nitride oxide fluoride

Solution

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Formula Ions Name

cation anion

NaCl Na+ Cl- sodium chloride

K2S K+ S2- potassium sulfide

MgO Mg2+ O2- magnesium oxide

CaI2 Ca2+ I- calcium iodide

Al2O3 Al3+ O2- aluminum oxide

Examples of Ionic Compounds with Two Elements

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Write the names of the following compounds:

1) CaO___________

2) KBr ___________

3) Al2O3___________

4) MgCl2 ___________

Learning Check

25

Write the names of the following compounds:

1) CaO calcium oxide

2) KBr potassium bromide

3) Al2O3 aluminum oxide

4) MgCl2 magnesium chloride

Solution

26

Metals That Form More Than One Cation

The name of metals

with two or more

positive ions

(cations) use a

Roman numeral to

identify ionic charge.

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Naming Ionic Compounds with Variable Charge Metals

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Naming Variable Charge MetalsTransition metals with two different ions use a Roman numeral after the name of the metal to indicate ionic charge.

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EXAMPLE: Naming FeCl2

To name FeCl2:1. Determine the charge of the cation using the subscript of the anion (Cl -).

Fe ion = 2+

2. Name the cation by the element name and add a Roman numeral in parentheses to show its charge.Fe2+ = iron (II)

3. Write the anion with an ide ending.

FeCl2 = iron(II) chloride

Remember Iron is a

Transition metal which is the reason for

the Roman numeral

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Learning Check

Select the correct name for each.1. Fe2S3

A) iron sulfide B) iron(II) sulfide C) iron(III) sulfide

2. CuO A) copper oxide B) copper(I) oxide C) copper(II) oxide

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SolutionSelect the correct name for each.A. Fe2S3

C) iron (III) sulfide Fe3+ S2-

B. CuO C) copper (II) oxide Cu2+ O2-