Chemical Bonding

Ionic, Covalent, and Metallic Bonding

Properties of Covalent Compounds

• ARE MOLECULAR…SMALLEST UNIT IS A MOLECULE

• USUALLY FORM BETWEEN TWO NONMETALS

• NONMETALLIC

• MAY BE SOLID, LIQUID OR GAS

• LOW MELTING POINT

• HIGH TO LOW SOLUBILITY IN WATER DEPENDING ON POLARITY

• SOLIDS ARE SOFTER THAN IONIC SOLIDS

• NONPOLAR COMPOUNDS DO NOT CONDUCT WHEN MOLTEN OR DISSOLVED. POLAR COMPOUNDS MAY CONDUCT WHEN DISSOLVED IN WATER

• EXAMPLES:– SUGAR– WAX– ALCOHOL– IODINE

Properties of Ionic Compounds

• COMPOSED OF POSITIVE AND NEGATIVE IONS

• SMALLEST PARTICLE IS AN ION

• FORM BETWEEN A METAL (+) AND A NONMETAL(-)

• ALL ARE CRYSTALLINE SOLIDS

• ARE ARRANGED IN AN ORDERLY FASHION TO FORM CRYSTALS

• HIGH MELTING POINTS

• BRITTLE

• HARD

• CONDUCT WHEN MELTED OR DISSOLVED

• EXAMPLES:– TABLE SALT– LYE (SODIUM HYDROXIDE)– POTASSIUM NITRATE

Properties of Metals

• LUSTER

• MALLEABILLITY

• DUCTILITY

• CRYSTALLINE

• SOLIDS AT ROOM TEMP. EXCEPT FOR MERCURY (Hg)

• MELTING POINTS VARY WIDELY

• GOOD CONDUCTORS OF HEAT& ELECTRICITY

• Examples: – Gold – Iron – Silver– Copper

Predicting Bond Types

Based on Compounds and Electronegativity

• IONIC BONDS OCCUR WHEN ELECTRONEGATIVITY DIFFERENCES BETWEEN THE TWO ATOMS ARE GREATER THAN 1.7

• METALS LOSE ELECTRONS AND FORM + IONS

• NONMETALS GAIN ELECTRONS AND FORM - IONS

• COVALENT BONDS FORM WHEN TWO ATOMS SHARE ELECTRONS

– NONPOLAR COVALENT BOND---EQUAL SHARING---• EN = 0.4 OR LESS

– POLAR COVALENT BOND---UNEQUAL SHARING---• EN = 0.41- 1.67

• IONIC BONDING OCCURS BETWEEN A METAL AND A NONMETAL

• COVALENT BONDING OCCURS BETWEEN 2 NONMETALS– NONPOLAR

• OCCURS BETWEEN 2 ATOMS OF THE SAME NONMETAL

– POLAR• OCCURS BETWEEN 2 DIFFERENT NONMETALS

• METALLIC BONDING OCCURS BETWEEN 2 METALS

PREDICTING BOND TYPE PRACTICE

USING ELECTRONEGATIVITY (chart pg. 169) AND

COMPOUNDS

What type of bond is represented by KF?

• Electronegativity– F: 4.0– K: 0.8

4.0-0.8= 3.2• Compounds

– K: metal– F: nonmetal

IONIC BOND

What type of bond is represented by O2?

• Electronegativity– O: 3.5– O: 3.5

3.5-3.5=0• Compounds

– O: nonmetal– O: nonmetal

NONPOLAR COVALENT BOND

What type of bond is represented by ICl?

• Electronegativity– I: 2.5– Cl: 3.0

3.0-2.5= 0.5• Compounds

– I: nonmetal– Cl: nonmetal

POLAR COVALENT BOND

What type of bond is represented by K2?

• Compounds– K: metal– K: metal

METALLIC BOND

Using your notes, predict the bond type of the following compounds as either ionic, polar covalent, nonpolar covalent, or metallic:

1. OH

2. N2

3. HF

4. CO

5. NaCl

6. H2

7. MgO

8. AlCl3

9. CH4

10. NF3

11. CS2

12. CCl4

13. SO3

14. Na2

15. Cl2

IONS

Octet Rule

States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons (the stable electron configuration of a noble gas).

Ions

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

– CATIONS (Positive Ions) • Low electronegativity; willing to give up electrons• Formed by metals losing electrons or giving electrons to

nonmetals• Losing electrons result in positive charges

– ANIONS (Negative Ions) • High electronegativity; electron loving• Formed by nonmetals gaining electrons from metals• Gaining electrons result in a negative charge

Determining the Ion

• Determine the number of valence electrons

• Draw Lewis Dot Structure

• Determine whether it would be easier to give away electrons or gain electrons– Trying to attain 8 electrons or a full shell

• Write the charge of the element based on the number of electrons gained or lost– Gaining electrons = - charge– Losing electrons = + charge

Gaining or Losing Electrons

• Any element with 4 or less valence electrons will give away their electrons

Losing electrons = positive charge

• Any element with 5-7 valence electrons will steal electrons

Gaining electrons = negative charge

Practice

• K

• Al

• S

• Mg

• O

• F

• Cu

• Ca

Day 2

Ionic Bonding

• CHEMICAL BONDS RESULTING FROM ELECTROSTATIC ATTRACTION BETWEEN POSITIVE AND NEGATIVE IONS

• REQUIRE THE LOST OF ELECTRON(S) BY ATOMS OF LOW ELECTRONEGATIVITY (METALS) TO ATOMS OF HIGH ELECTRONEGATIVITY(NONMETALS)

• REQUIRE AN ELECTRONEGATIVITY DIFFERENCE GREATER THAN 1.7

Examples

• NaCl

• MgO

• AlCl3

• CCl4

Ionic Bonding Practice• Draw the Lewis structure of

each element

• Circle the element donating electrons

• Underline the element receiving the electrons

• Draw the arrow(s) to show the transfer of electrons

• Write each element as an ion

• KF

• MgI

• BeS

• NaO

• AlBr

• LiBr

• BaS

• CsP

Metallic Bonding

• RESULTS FROM THE ATTRACTION BETWEEN METAL ATOMS AND THE SURROUNDING SEA OF ELECTRONS

• FORMS BETWEEN 2 METAL ATOMS

• BONDING ELECTRONS ARE DELOCALIZED ALONG EMPTY P OR D ORBITALS

• STRENGTH OF BOND VARIES WITH NUCLEAR CHARGE OF THE METAL

Covalent Bonding

• FORMS WHEN A PAIR OF E- ARE SHARED

• FORM MOLECULES

• SHARING MAY BE EQUAL…NONPOLAR OR UNEQUAL…POLAR

• SINGLE COVALENT BOND FORMS WHEN TWO ATOMS SHARE A PAIR OF E-

• DOUBLE COVALENT BOND FORMS WHEN 2 ATOMS SHARE 2 PAIRS OF E-

• TRIPLE COVALENT BOND FORMS WHEN 2 ATOMS SHARE 3 PAIRS OF E-

• SIGMA BOND…FORMED BY DIRECT OVERLAP OF TWO ORBITALS

• PI BOND…FORM WHEN 2 P ORBITALS OVERLAP SIDE-TO-SIDE WITH THEIR AXIS PARALLEL

• SINGLE BOND IS ALWAYS A SIGMA BOND

• DOUBLE BOND CONSISTS OF ONE SIGMA BOND AND ONE PI BOND

• TRIPLE BOND CONSISTS OF ONE SIGMA BOND AND TWO PI BONDS

• ONLY 4 ELEMENTS COMMONLY FORM DOUBLE OR TRIPLE BONDS: C, S, N, O

Examples of Covalent Bonds

HCl

Diatomic Gases (7)

• Diatomic: 2 atoms– Prefix di means 2

• Occur in nature as diatomic molecules instead of single atoms because they are more stable than individual atoms

• Hydrogen (H2)

• Oxygen (O2)

• Nitrogen (N2)

• Fluorine (F2)

• Chlorine (Cl2)

• Bromine (Br2)

• Iodine (I2)

Examples of Covalent Bond in Diatomic Molecule

Br2

Covalent Bonding

• Draw the Lewis structure of each element

• Circle the electrons being shared

• Draw each compound

• HF

• CCl4

• SeI2

• H2S

• NBr3

Homework

Textbook pg. 220: 12-16

& pg. 247: 6-10 & 12a-e

Day 3

Molecular Shapes

• 3 ways to predict the shape of molecules

– Build the model

– VSEPR

• Valence Shell Electron Pair Repulsion Theory

– Hybridization

Building Models

Physical Model

Computer Generated Model

Hybridization

A process in which atomic orbitals are mixed to form new identical

hybrids

VSEPR

• REPULSION BETWEEN VALENCE ELECTRONS CAUSES ELECTRON PAIRS TO SPREAD AS FAR APART AS POSSIBLE

• UNSHARED PAIRS OCCUPY MORE SPACE THAN SHARED PAIRS.

• THEORY GIVES SHAPE AND BOND ANGLE. SEE VSEPR CHART pg. 260

Polarity of Molecules

• MUST CONTAIN AT LEAST ONE POLAR BOND & BE ASSYMETRIC

• ARE CALLED DIPOLES BECAUSE THEY HAVE A POSITIVE END AND A NEGATIVE END

– Symmetrical = nonpolar molecule– Asymmetrical = polar molecule

Draw the following molecules and determine their polarity and

shape :• NF3

• SiF4

• H2Se

• SeCl2

• BF3

• GeF4

• H2S

• CF4

• SCl2

• NH2Cl

Intermolecular Forces

In order of decreasing strength:

Hydrogen Bonds

Dipole-Dipole Forces

London Dispersion Forces

Hydrogen Bonding

• A strong dipole-dipole attraction between molecules that contain a hydrogen atom bonded to a small, extremely electronegative atom with at least one lone pair of electrons

– attraction between molecules when H is bonded to O, N, or F

• Ex. H2O

Dipole-Dipole Forces

• the attractions between oppositely charged region of polar molecules

• Ex. BCl3

London Dispersion Forces

• the weak forces resulting from temporary shifts in the density of electrons in electron clouds

• electrons of one molecule attracted to nucleus of another molecule

• Ex. H2