Chemical Bonds
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Chemical Bonds. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons. Gain 4 electrons. C would like to N would like to O would like to. Gain 3 electrons. Gain 2 electrons. Electron Dot Structures.

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Chemical Bonds

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Chemical Bonds

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

Gain 4 electrons

  • C would like to

  • N would like to

  • O would like to

Gain 3 electrons

Gain 2 electrons

Electron Dot Structures

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

1 2 13 14 15 16 17 18

H He:

    

LiBe B  C  N  O : F :Ne :

     

    

Na Mg AlSiPS:Cl  :Ar :

   

Chemical bond

  • A chemical bond forms when outer-shell electrons of different atoms come close enough to each other to interact and rearrange themselves into a more stable arrangement.

Types of Chemical Bonds

  • Ionic bonds formed when metal atoms combined with non-metal atoms

    • Metallic bonds formed when metal atoms combined with metal atoms.

    • Covalent bonds formed when non-metal atoms combined with non-metal atoms.

Ionic Compounds

1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

The coordination number of an ionic lattice is written

as a ratio x:y

How many chlorine ions surround

each sodium ion and vice versa?

NaCl coordination number- 6:6

Hardness and Brittleness

  • Figure 6.4 The repulsion between like charges causes this sodium chloride crystal to shatter when it is hit sharply.

Electrical Conductivity

  • In the solid form, ions in sodium chloride are held in the crystal lattice and are not free to move so cannot conduct electricity.

  • When the solid melts the ions are free to move.

  • In a similar way, when sodium chloride dissolves in water, the ions separate and are free to move towards the opposite charge.

Properties of Ionic Compounds

  • Forms crystal composed of 3d array of ions (ionic network lattice)

  • Have high melting and boiling temperatures.

  • Are hard but brittle

  • Do NOT conduct electricity in the solid state

  • They will only conduct electricity if they are melted or dissolved in water.


  • From the properties we can conclude:

    • The forces between the particles are strong.

    • There are no free-moving electrons present, unlike in metals.

    • There are charged particles present, but in solid state they are not free to move.

    • When an ionic compound melts, however, the particles are free to move and the compound will conduct electricity.

Use Electron shell diagram and simple equation to show the formation of:

  • NaCl

  • MgO

Naming Binary Ionic CompoundsContain 2 different elements

  • Name the metal first, then the nonmetal as -ide.


    NaClsodium chloride

    ZnI2zinc iodide

    Al2O3aluminum oxide


Complete the names of the following binary compounds:



Al2O3 ________________



Complete the names of the following binary compounds:

Na3Nsodium nitride

KBrpotassium bromide

Al2O3aluminum oxide

MgSmagnesium sulfide

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 ion copper (II) ion iron(III) ion


zinc ion

Write symbols for these:

  • Potassium ion

  • Magnesium ion

  • Copper (II) ion

  • Chromium (VI) ion

  • Barium ion

  • Mercury (II) ion

Formula of ionic compounds

Criss-Cross Method

  • Write the symbols for the ions side by side. Write the cation first.

    • Al3+O2-

  • Cross over the charges by using the absolute value of each ion’s charge as the subscript for the other ion.

    • Al2O3

  • 3. Check the subscripts and divide them by their largest common factor to give the smallest possible whole-number ratio of ions. Then write the formula.

    • Al2O3

      • For Al: 2 x 3+ = 6+For O: 3 x 2- = 6-

Criss-Cross Method

Example 1: Calcium and Oxygen









Criss-Cross Method

Example 2: Magnesium and Phosphorus








  • The sum of the cation charge and the sum of the anion charge must cancel each other so that the compound formed is neutral.


1. The formula for the ionic compound of

Na+ and O2- is

1) NaO2) Na2O3) NaO2

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

1) Al3Cl2) AlCl23) AlCl3

3. The formula of Fe3+ and O2- is

1) Fe3O22) FeO33) Fe2O3


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

Sample Problem 7-1

  • Write the formulas for the binary ionic compounds formed between the following elements:

    A. lithium and fluorine

    B. lithium and oxygen

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) chloride

SnF4 (Sn4+)tin (IV) fluoride

PbCl2 (Pb2+)lead (II) chloride

Fe2S3 (Fe3+)iron (III) sulfide

II. Stock system (roman numerals)

  • Example:



  • Iron(II)

  • Iron(III)



  • copper(I) chloride

  • copper(II) chloride

Sample Problem 7-2

a. Write the formula and give the name for the compound formed from the ions Cr3+ and F-.

b. Write the name for Cu3N2.

Here are the changes in the electronic structure of iron to make the 2+ or the 3+ ion.

Learning Check

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

FeBr2iron (_____) bromide

Cu2Ocopper (_____) oxide

SnCl4___(_____ ) ______________




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

FeBr2iron ( II ) bromide

Cu2Ocopper ( I ) oxide

SnCl4tin (IV) chloride

Fe2O3iron (III) oxide

CuScopper (II) sulfide

Learning Check

Name the following compounds:

A. CaO

1) calcium oxide2) calcium(I) oxide

3) calcium (II) oxide

B. SnCl4

1) tin tetrachloride2) tin(II) chloride

3) tin(IV) chloride

C. Co2O3

1) cobalt oxide 2) cobalt (III) oxide

3) cobalt trioxide


Name the following compounds:

A. CaO1) calcium oxide

B. SnCl43) tin(IV) chloride

C.Co2O32) cobalt (III) oxide

Learning Check

Write the correct formula for the compounds containing the following ions:

A. Na+, S2-

1) NaS 2) Na2S3) NaS2

B. Al3+, Cl-

1) AlCl3 2) AlCl 3) Al3Cl

C. Mg2+, N3-

1) MgN 2) Mg2N33) Mg3N2


A. Na+, S2-

2) Na2S

B. Al3+, Cl-

1) AlCl3

C. Mg2+, N3-

3) Mg3N2


Name the following ionic compounds:

Na2O K2S MgBr2 AlN Ba3As2

CaCl2 AgCl AlH3 ZnI2 Li3P

Nomenclature of binary ionic compounds


Na2O = sodium oxide K2S = potassium sulfide

MgBr2 = magnesium bromide AlN = aluminum nitride

Ba3As2 = barium arsenide CaCl2 = calcium chloride

AgCl = silver chloride AlH3 = aluminum hydride

ZnI2 = zinc iodideLi3P = lithium phosphide

III. Polyatomic Ions

  • A charged group of covalently bonded atoms

    • Combine with ions of opposite charge to form ionic compounds

  • Ex: NH4+, NO3-, SO42-

Nomenclature of binary ionic compounds

Some polyatomic anions that you must know:

NO3- = nitrateNO2- = nitrite

SO4 2- = sulfateSO32- = sulfite

PO43- = phosphatePO33- = phosphite

CO32- = carbonate

HCO31- = hydrogen carbonate or bicarbonate

OH- = hydroxideCN- = cyanide

C2H3O2- = acetateC2O42- = oxalate

III. Polyatomic Ions

  • Most common ion is given the ending –ate.

  • One less oxygen than –ateends in–ite.

  • One less oxygen than –iteis given the prefixhypo.

  • One more oxygen than -ateis given the prefixper.





  • perchlorate

  • chlorate

  • chlorite

  • hypochlorite



  • nitrate

  • nitrite

Sample Problem 7-3

a. Write the formula for potassium sulfate.

b. Write the formula for calcium carbonate.

c. Write the formula for tin(IV) sulfate.

Ionic Nomenclature Practice

  • potassium chloride

  • magnesium nitrate

  • copper(II) chloride


  • K+ Cl-

  • Mg2+ NO3-



  • Cu2+ Cl-

Nomenclature of binary ionic compounds

Naming salts composed of the polyatomic ions is the same as with the monatomic anions. Metal name then polyatomic name.

NaOH sodium hydroxideBa(NO3)2 barium nitrate

H2SO4 hydrogen sulfateCsNO2 cesium nitrite

Sometimes there is a common name:

KHCO3potassium hydrogen carbonate or potassium bicarbonate

  • Note: the polyatomic anions must be memorized.

Name the following ionic compounds:


Ca(OH)2 NH4NO3Zn(NO3)2 Li3PO4 HNO3

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