Ch. 7 Ionic Bonds

Chemical Bonds

•Chemical bonds form when atoms are strongly attracted to one another

1) Ionic Bond2) Covalent Bond3) Metallic Bond

Compounds - Review•Compound: Substance that is composed of two or more

elements that are combined chemically •Properties of a compound are generally very different

from the elements that make it • Chemical Formulas:

• Formulas show the symbols on the ration of the elements in the compound

• Subscripts: tell the number of each element in the compound

Ex. C12H22O11

Review:

•Valence Electrons: Electrons in the highest energy level • The number of valence electrons largely determines the

chemical properties of an element. • To find the number of valence electrons, look at its group

number.

• Electron Dot Notation: represents the number of valence electrons

Ions - Review

• Ion: an atom or bonded group of atoms that has a positive or negative charge

• When atoms lose electrons and become positive ions, they always become smaller (compared to the neutral atom)• Loss of valence electron can leave an empty outer orbital resulting in a small

radius

• When atoms gain electrons and become negative ions, they become larger

Octet Rule

• Atoms tend to gain, lose (ionic bond) or share (covalent bond) electrons until they are surrounded by eight valence electrons

• An octet consists of 8 valence electrons

• Since the noble gases have eight electrons, we assume that an atom is stable when surrounded by 8 valence electrons

A gain of one electron gives chlorine an octet and converts a chlorine atom into a chloride ion. It has the same electron configuration as the noble gas argon.

Ionic Bond

• Type of chemical bond

• Electron transfers lead to forces holding atoms together

• Binds opposite charged ions together

• Formed by a METAL and a NONMETAL (or a group)

• Examples: NaCl (Sodium Chloride), Na2CO3 (Sodium Carbonate)

**To determine is an element is a metal, nonmetal or metalloid, look at its placement on the periodic table.

Ionic Bonding

• A bond forms when oppositely charged atoms are electrostatically attracted to one another as a result of the transfer of electrons

Classes of Ionic Bonds

1. Oxides • Compounds with ionic bonds between a metal and

oxygen• Example: MgO (Magnesium Oxide)

2. Salts • Generic name for most ionic compounds • Examples: NaCl (Sodium Chloride), ZnI2 (Zinc Iodide)

Intro to Ionic Names & Formulas

• Monatomic Ions: one-atom ions 1) Cation

• Positive ion formed by the loss of valence electrons

• Atom loses electrons to have an octet like the previous noble gases

• Naming: The cation name stays the same as the atom name • Example: Li Lithium

Li+ Lithium Ion

Monatomic Ions

2) Anion •A Negative ion formed by the gain of electrons •Atoms gain electrons to achieve an octet •Naming: For the anion, add the suffix –ide to the

root of the atom name• Example: Br bromine, Br - Bromide Ion

Oxidation Number (Oxidation State)

• The charge of a monatomic ion

• The number of electrons gained or lost to make an ion

• Monatomic Ion Trends: • Group 1: Plus 1 charge

• Group 2: Plus 2 charge

• Group 17: Negative 1 charge

• Group 16: Negative 2 charge

• Group 15: Negative 3 charge

Practice:

Write the symbol, name of the ion, and determine if it’s a cation or anion.

1. An iodine atom gains one electron

2. A strontium atom loses two electrons

3. A sulfur atom gains two electrons

4. An aluminum atom loses three electrons

Practice:

Atoms that tend to gain a noble gas configuration by LOSING valence electrons are

A. Metals

B. Nonmetals

C. Noble Gases

D. Representative Elements

Polyatomic Ions

• Polyatomic Ions:• Ions made up of more than one atom • Charge applies to the whole group • Never change the subscripts of atoms within the ion

• Example: CO32- (Carbonate)

• Oxyanion: • Ion with a nonmetal and one or more oxygen atoms

Polyatomic Ion Trends

NamingElement: S SulfurAnion: S2- Sulfide

SO52- Persulfate (+1 oxygen)

SO42- Sulfate

SO32- Sulfite (-1 oxygen)

SO22- Hyposulfite (-2 oxygen)

Ionic Bonds

• Ion Bond: Metal and Nonmetal Or

Positive Ion and Negative Ion

• When atoms transfer electrons, the atoms become bonded and form ionic compounds

• Although they are composed of charged ions, ionic compounds are electrically neutral (positive charge = negative charge).

Ionic Nomenclature

Writing Ionic Compound Formulas:

1. Write the cation and anion formulas with charges

2. Balance the charges with subscripts if necessary

3. Use parentheses around polyatomic ions that need a subscript added

4. Write the final neutral formula without charges

Practice:

•Potassium Permanganate: K+ MnO4

- KMnO4

•Aluminum Oxide:Al3+ O2-

add Al3+ Al3+ O2- O2- O2-Al2O3

•Copper (II) Hydroxide: Cu2+ OH-

add OH- Cu(OH)2

More Practice:

•Sodium Phosphate:

• Iron (III) Sulfate:

•Calcium Manganate:

Na3PO4

Fe2(SO4)3

CaMnO4

Naming Ionic Compounds

1. Cation name written first

2. Anion name written second

**Reminder: Use the roman numerals for most cations

Practice:

•Li3PO4 -- lithium phosphate

•Fe(ClO4)2 -- iron (II) perchlorate

•Na2SO4 – sodium sulfate

More Practice:

•(NH4)2S

•AgC2H3O2

•CuCl

•LiHCO3

Ammonium Sulfide

Silver Acetate

Copper (I) Chloride

Lithium Bicarbonate

Properties of Ionic Compounds

• Crystal Lattice:

• Ions are arranged in a regular, repeating 3D pattern

• Each +ion is surrounded by – ions

• Overall the shape of the crystal depends on the relative number of + ions and – ions

Crystal Structure

Properties of Ionic Compounds

• Physical Properties:

• Particles are highly attracted to one another

• High melting & boiling points• Ionic crystals are hard, rigid, and

brittle• Can conduct electrical currents

• Electrolyte: an ionic compound whose aqueous solution conducts electricity• Aqueous Solutions: A substance

dissolved into water