Ch.5 (Types of compound )Section 1(Ionic Compound)

Gr.10 /Chemistry/LC3

Nagham Hussam Chemistry Teacher

Ionic compoundsIonic compounds

are:1. Made up of

oppositely charged ions held together strongly in well-organized units.

2. Hard solids at room temperature and are difficult to melt. Look at the structure of magnesium oxide.

The smallest part of compounds Molecule: the smallest unit of

the compound in a covalent compound.

Formula unit The simplest ratio of ions in a compound.

Binary Ionic Compounds

You will learn how to name and write formulas for ionic

compounds.Binary compound: a

compound that contains only two elements.

Ex: Sodium chloride (NaCl), potassium iodide (KI) and (CaF2) calcium florid (contain more than one ion of each element)

 

Predicting Charge on Ions

Metals have few outer-level electrons so they tend to lose them and become positive ions.

Sodium must lose just one electron, becoming a Na+ ion.

Calcium must lose two electrons, becoming a Ca2+ ion.

The charge on the ion is known as the oxidation number of the atom.

The oxidation numbers for many elements in the main groups are arranged by group number.

Predicting Charge on Ions

Oxidation numbers for elements in Groups 3 through 12, the transition elements, cannot be predicted by group number.

Aluminum is in Group 13, so it loses its three outer electrons to become an Al3+ ion; oxygen is in Group 16 and has six valence electrons, so it gains two electrons to become an O2– ion.

How to name a binary ionic compoundTo name a binary ionic compound,

first write the name of the positively charged ion, usually a metal, and then add the name of the nonmetal or negatively charged ion, whose name has been modified to end in -ide.

Magnesium combines with oxygen to form a compound called magnesium oxide (MgO).

How to write the formula Sodium chloride contains sodium ions

that have a 1+ charge and chloride ions that have a 1– charge.

the sum of the charges in an ionic compound must always equal zero.

Learning Check

Write the correct formula for the compounds containing the following ions:A. Na+, S2-

1) NaS 2) Na2S 3) NaS2

B. Al3+, Cl-

1) AlCl3 2) AlCl 3) Al3Cl

C. Mg2+, N3-

1) MgN 2) Mg2N3 3) Mg3N2

Solution

A. Na+, S2-

2) Na2S

B. Al3+, Cl-

1) AlCl3

C. Mg2+, N3-

3) Mg3N2

Naming Binary Ionic CompoundsContain 2 different elementsName the metal first, then the

nonmetal as -ide.Examples:

NaCl sodium chlorideZnI2 zinc iodide

Al2O3 aluminum oxide

Learning Check

Complete the names of the following binary compounds:Na3N sodium ________________

KBr potassium ________________

Al2O3 aluminum

________________

MgS _________________________

Solution

Complete the names of the following binary compounds:

Na3N sodium nitride

KBr potassium bromide

Al2O3 aluminum oxide

MgS magnesium sulfide

Learning Check

A. The formula for the ionic compound of

Na+ and O2- is 1) NaO 2) Na2O 3) NaO2

B. The formula of a compound of aluminum and chlorine is

1) Al3Cl 2) AlCl2 3) AlCl3

C. The formula of Fe3+ and O2- is 1) Fe3O2 2) FeO3 3)

Fe2O3

Solution

A. The formula for the ionic compound of

Na+ and O2- is

2) Na2O

B. The formula of a compound of aluminum and chlorine is

3) AlCl3

C. The formula of Fe3+ and O2- is

3) Fe2O3

Transition Metals

Many form 2 or more positive ions

1+ 2+ 1+ or 2+

2+ or 3+

Ag+ Cd2+ Cu+, Cu2+ Fe2+, Fe3+

silver cadmium copper(I) ion

iron(II) ion ion copper (II) ion

iron(III) ion

Zn2+

zinc ion

Names of Variable Ions

Use a roman number after the name of a metal that forms two or more ions

Transition metals and the metals in groups 4A and 5A

FeCl3 (Fe3+) iron (III) chloride

CuCl (Cu+ ) copper (I) chlorideSnF4 (Sn4+) tin (IV) fluoride

PbCl2 (Pb2+) lead (II) chloride

Fe2S3 (Fe3+) iron (III) sulfide

Learning Check

Complete the names of the following binary compounds with variable metal ions:

FeBr2 iron (_____) bromide

Cu2O copper (_____) oxide

SnCl4 ___(_____ ) ______________

Fe2O3 ________________________

CuS ________________________

Solution

Complete the names of the following binary compounds with variable metal ions:

FeBr2 iron ( II ) bromide

Cu2O copper ( I ) oxide

SnCl4 tin (IV) chloride

Fe2O3 iron (III) oxide

CuS copper (II) sulfide

Learning Check Name the following compounds:A. CaO

1) calcium oxide 2) calcium(I) oxide

3) calcium (II) oxide

B. SnCl4 1) tin tetrachloride 2) tin(II)

chloride 3) tin(IV) chloride

C. Co2O3

1) cobalt oxide 2) cobalt (III) oxide

3) cobalt trioxide

Solution

Name the following compounds:A. CaO 1) calcium oxide

B. SnCl4 3) tin(IV) chloride

C. Co2O3 2) cobalt (III) oxide

Compounds Containing Polyatomic Ions

Polyatomic ion: An ion that has two or more different elements.

Compounds Containing Polyatomic Ions

Compounds Containing Polyatomic IonsIonic compounds may contain:1. positive metal ions bonded to negative

polyatomic ions, such as in NaOH .

2. negative nonmetal ions bonded to positive polyatomic ions, such as in NH4I .

3. or positive polyatomic ions bonded to negative

polyatomic ions, such as in NH4NO3.

How to write formula of Compounds Containing Polyatomic Ions

Remember that the sum of the positive and negative charges must equal zero.

Write a subscript outside the parentheses to show the number of polyatomic ions in the compound.

The formula for the compound that contains one magnesium ion and two nitrate ions is Mg (NO3)2.

How to name a compound containing a polyatomic ionTo name a compound

containing a polyatomic ion, follow the same rules as used in naming binary compounds.

The name of the compound composed of calcium and the carbonate ion is calcium carbonate.

To form a neutral compound, one Ca2+ ion must combine with one CO3

2– ion to give the formula CaCO3.

Hydrates

Hydrate: A compound in which there is a specific ratio of water to ionic compound. For example CaSO4 • 2H2O is calcium sulfate dihydrate.

Hygroscopic: compounds can easily become hydrates by absorbing water molecules from water vapor in the air. Example is Sodium Carbonate (Na2CO3).

Hydrates

Deliquescent: Substances those are so hygroscopic that they take up enough water from the air to dissolve completely and form a liquid solution.

HydratesThe dot in the formula

represents a ratio of compound formula units to water molecules.

For example, CaSO4 • 2H20 is the formula for a hydrate of calcium sulfate that contains two molecules of water for each formula unit of calcium sulfate.

How To name hydratesTo name hydrates, follow the

regular name for the compound with the word hydrate, to which a prefix has been added to indicate the number of water molecules present.

The name of the compound with the formula CaSO4 • 2H2O is calcium sulfate dihydrate.

Anhydrous compoundHeating hydrates can drive off the

water. This results in the formation of an

anhydrous compound—one in which all of the water has been removed.

In some cases, an anhydrous compound may have different color from that of its hydrate. For example: CuSO4.5H2O is (blue) while anhydrous of CuSO4 is (white)

Good luck