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Unit 4 Bonding Notes

Atoms are generally found in nature in combination held together by _______________

____________ .

A chemical bond is a _______________________________ between the nuclei and

valence electrons of different atoms that binds the atoms together

There are three main types of bonding: __________, ___________ and __________.

Ionic Bonding occurs between a ______________ and a ______________.

Metallic bonding occurs between two ____________________.

Covalent bonding occurs between a ______________ and a ______________.

A positive ion is called a _____________________________.

A negative ion is called an_____________________________.

What determines the type of bond that forms?

The ______________________ of the two atoms involved are redistributed to the

___________________________________________.

The interaction and rearrangement of the _______________________ determines

which type of bond that forms.

Before bonding the atoms are at their highest possible _______________________.

There are __________ philosophies of atom to atom interaction.

One understanding of the formation of a chemical bond deals with balancing the

opposing forces of _____________________________________.

Repulsion occurs between the _________________

-

clouds of each atom.

Attraction occurs between the __________________ and the negative electron clouds.

When two atoms approach each other closely enough for their electron clouds to begin

to overlap

The electrons of one atom begin to

_______________ the electrons of the other atom

Name _________________________

Block _________

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And repulsion occurs between the _______________ of the two atoms.

As the optimum distance is achieved that balances these forces, there is a release of

potential energy

The atoms _________________ within the window of maximum attraction/minimum

repulsion

The _______________ released the stronger the _______________ bond between the

atoms

Another understanding of the formation of a chemical bond between two atoms centers

on achieving the most __________________________ of the atoms’ valence electrons

By rearranging the electrons so that each atom achieves a ______________________

________________ ________________ creates a pair of stable atoms (____________

___________________________________)

Sometimes to establish this arrangement one or more valence electrons are ________

______________________________________________.

Basis for _________________ bonding

Sometimes valence electrons are _______________________________________

Basis for _____________________ bonding

A good predictor for which type of bonding will develop between a set of atoms is the

difference in their __________________________________________..

Remember, electro-negativity is a measure of the ______________________ an atom

has for e-s after developing a bond

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The _________________________ the difference between the two atoms, __________

___________________________________________________ of electrons

Let’s consider the compound Cesium Fluoride, _______________.

The electro-negativity value (EV) for Cs is ____________; the EV for F is ___________.

The difference between the two is _____________, which falls within the scale of ionic

character.

When the electro-negativity difference between two atoms is greater than

______________________________________.

The take home lesson on electro-negativity and bonding is this:

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The ________________________ are on the P.T., the more evenly their e--

interact, and

are therefore more likely to form a _______________________

The ________________________________ are on the P.T., the less evenly their e

-

interact, and are therefore more likely to form an ionic bond.

Forming ionic bonds can be represented as _____________________________.

Hint - metal w/nonmetal = ionic nonmetal w/nonmetal = covalent

Covalent Bonding

In a Covalent bond:

The ___________________________ between the atoms involved is not extreme

So the interaction between the involved electrons is ____________________________

It may not be an equal sharing relationship, but at least the electrons are being

“___________________”.

Covalent bonds are between _____________________________________________.

Covalent bonds are formed when electrons are _____________________ between two atoms.

If two atoms share 2 electrons, they form a _____________________________. If two

atoms share 4 electrons, they form a _____________________________.

If two atoms share 6 electrons, they form a ____________________________.

There are two types of covalent bonds: polar and non-polar. Polar bonds usually involve

__________________________________. Non-polar bonds usually involve

___________________________________.

In polar bonds, the electrons are shared ________________________________. In non-

polar bonds, the electrons are shared ________________________________.

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Covalent compounds can exist in any state (solid, liquid or gas). They have

_____________ melting and boiling points.

A ____________________ is a diagram showing the arrangement of valence electrons

among the atoms in a molecule.

We use ______________ to represent valence electrons involved in bonding.

______________________ are electrons present in the outermost energy level of an atom.

Examples of Lewis Dot Symbol

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Recall that the valence electrons for the elements can be determined based on the

elements position on the ________________.

Atoms can _________________ more than one electron pair.

They may double or triple up pairs of electrons to satisfy the _________________.

A _______________________ is the sharing of one pair of electrons between two

atoms.

A __________________________ is the sharing of ______ pairs of electrons between

two atoms.

A ____________________ is the sharing of _______ pairs of electrons between two

atoms.

_____________ element can form depends on the number of valence electrons.

Rules for Writing Lewis Structures

Determine whether the compound is __________________________. If covalent, treat

the entire molecule. If ionic, treat each ion separately.

Determine the __________ number of _______________ _________________ available

to the molecule or ion by summing the valence electrons of all the atoms in the unit.

Organize the atoms so there is _______________ ____________________ (usually the

least electronegative) surrounded by ligand (outer) atoms. Hydrogen is never the central

atom.

So what is the bottom line? To be stable the two atoms involved in the covalent bond

share their electrons in order to achieve the arrangement of a ________________.

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Ionic Bonds

In an Ionic bond:

The electro-negativity difference is ____________________,

So the atom with the _______________________ pull doesn’t really share the electron

Instead the electron is essentially ___________________________________________

_______________________________________________________________________

When a metal bonds with a nonmetal, an bond is

formed.

An ionic bond always involves the TRANSFER of electrons from the

to the .

The cation and anion are held together by ___________________________________.

An ionic compound does not consist of individual molecules. Instead, there is a huge

network of positive and negative ions that are packed together in a

.

Because their bonds are so strong, ionic compounds tend to have very

_________________ points.

Ionic compounds are _____________________________, which means they can

conduct electricity.

When forming ionic compounds the positive and negative charges must

_____________.

_______________________________________________________________________

_______________________________________________________________________ .

An electron is _______________________ from the sodium atom to the chlorine atom.

The bottom line is, to be stable the two atoms involved in the ionic bond will either

___________________ or _________________ their valence electrons in order to

achieve a stable __________________ arrangement of electrons.

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Metallic Bonding

Metallic bonds consist of positively charged metallic cations that donate electrons to the

__________________.

The “sea” of electrons are shared by all atoms and can move throughout the structure.

Properties:

o Thermal Conductivity o Electrical Conductivity o Malleability- the ability to be hammered down into thin sheets. o Ductility- the ability to be drawn into a wire.

In a metallic bond:

The resulting bond is a cross between ____________ and _____________ bonding

Valence electrons are transferred from one metal atom to the __________________ metal

atoms

But none of the involved metal atoms want the electrons from the original atom, nor their

own so they ___________________________________

What results is a ________________________________ of valence electrons that none

of the atoms in the collection ________________ the valence electrons

It resembles collection of positive ions floating around in a sea of electrons

Determining the Type of Bond: Determine the type of bond (Ionic, Covalent or Metallic) in the following compounds:

Compound Bond Type Compound Bond Type

NaCl NCl3 CO PF3

FeNi CaCl2

SiS2 Fe2O3

End of PPT 1

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Draw the Lewis structures for the following compounds: 1) PBr3 4) NO2

-1 2) N2H2 5) C2H4 3) CH3OH 5) HBr Determine if the elements in the following compounds are metals or non-metals. Describe

the type of bonding that occurs in the compound.

Compound Element 1 (metal or non-metal?)

Element 2 (metal or non-metal?)

Bond Type

NO2 N = non-metal O = non-metal covalent

NaCl

SO2

PO43-

MgBr2

CaO

H2O

Cu-Zn alloy

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Rules of writing formulas:

· positive ion is written first … this is usually a metal

· negative ion is written second … this is usually a nonmetal

· subscripts are used to show how many ions of each part are in the compound. They

are used to balance the charge of the ions. · criss-cross method:

Examples:

1. sodium oxide

sodium is the positive ion = +1

oxide is the negative ion = -2

therefore … it takes 2 sodium ions to balance the charge of the oxide

Formula = Na2O

2. calcium nitrate

calcium is the positive ion = +2

nitrate is the negative ion = -1

therefore … it takes 2 nitrates to balance the charge of calcium

Formula = Ca(NO3)2

3. aluminum sulfide

aluminum is the positive ion = +3

sulfide is the negative ion = -2

therefore … it takes 2 aluminum ions and 3 sulfide to balance the charge

Formula = Al2S3

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Covalent Naming

Binary covalent compounds are characterized by having two nonmetals. Naming these compounds involves the use of numerical prefixes:

Prefix Number Prefix Number

1 6

2 7

3 8

4 9

5 10

If there is only ONE atom of the first element, you DON’T need a prefix. The FIRST element is named as a normal element. The SECOND element has an –IDE ending.

o N2O4

o XeF4

o N2O5

o CO

o CBr4

Diarsenic pentoxide

o Phosphorous pentabromide

o Carbon tetraiodide

o Trisilicon tetranitride

o Tetraphosphorous decoxide

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Write the correct formulas for each covalent compound:

Compound Name Oxidation States Covalent Formula

water O (-2) H (+1)

Carbon Dioxide C (+4) O (-2)

Chlorine (Diatomic Element) Cl (-1)

Methane (5 total atoms) C (-4) H (+1)

Ammonia (4 total atoms) N (-3) H (+1)

Carbon tetrabromide (5 total atoms)

C (+4) Br (-1)

Phosphorous trichloride (4 total atoms)

P (-3) Cl (-1)

Diphosphorous trioxide (5 total atoms)

P (-3) O (-2)

Balancing Charges

Criss-Cross rule

1. Write out symbols and charge of elements

2. Criss-Cross charges as subscripts (Swap and Drop)

3. Combine as a formula unit

Equation Form of Balancing Charges (Number of Cations)x(Cation Charge) + (Number of Anions)x(Anion Charge) = 0 (1)(+3) + (X)(-1) = 0, x = 3

o EX: Aluminum and Oxygen EX: Barium and Oxygen

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Balancing Charges Practice:

o Lithium Iodide

o Strontium Chloride

o Sodium Sulfide

In each box, write the formula of the ionic compound consisting of the positive ion to the left of the box and the negative ion above the box.

Cl- S

-2 F N-3 O P

-3

Mg+2

Cs+

Cr+3

Na

Zn+2

Al+3

K

I have provided you with charges on some but not all the elements above.

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Valence Shell Electron Pair Repulsion Theory (VSEPR Theory).

This is the way that we predict the geometry shape of molecules, A model was developed a

qualitative model known as Valence Shell Electron Pair Repulsion Theory (__________________

Theory).

The basic assumptions of this theory are summarized below.

1) The electron pairs in the valence shell around the central atom of a molecule repel each other

and tend to orient in space so as to minimize the repulsions and maximize the distance between

them.

2) There are two types of valence shell electron pairs: ______________ pairs and

________________ pairs

Bond pairs are ______________ _________________ by two atoms and are attracted by two

nuclei. Hence they occupy less space and cause less repulsion.

Lone pairs ________________ ______________ involved in bond formation and are in

attraction with only one nucleus. Hence they occupy more space. As a result, the lone pairs

cause more repulsion.

Note: The bond pairs are usually represented by a ___________ _______________, whereas

the lone pairs are represented by a lobe with two electrons.

3) In VSEPR theory, the ___________________ bonds are treated as if they were single bonds. The

electron pairs in multiple bonds are treated collectively as a single super pair.

4) The shape of a molecule can be predicted from the number and type of valence shell electron

pairs around the central atom.

When the valence shell of central atom contains only bond pairs, the molecule assumes

symmetrical geometry due to even repulsions between them.

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VSPER- Valence Shell Electron Pair Repulsion

Bonds Lone Pairs Shape

Linear

Bent

Trigonal Planar

Trigonal Pyramidal

Tetrahedral

Steric number is the total number of ______________________________ AND ______________________.

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VSEPR Practice Complete the table with the requested information.

Molecule Structural Diagram Oxidation State of each element

Molecular Geometry

CClF3

SF2

BF3

SiBr4

NH3

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Bonding Notes Activity:

Formula Bond Type

(Ionic/Covalent)

Lewis

Structure

Shared

Electron

Pairs

Lone

Electron

Pairs

Total

Electron

Pairs

Shape Structural

Formula

NaCl

NH3

SCl2

CH4

PCl3

MgCl2

CO2

SiBr4

H2O

BCl3

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Polarity Bond Polarity

Electronegativity Ionic bonds have an electronegativity difference that is greater than 1.7. Covalent bonds have an electronegativity difference less than (or equal to) 1.7. Electronegativity differences between 0 and 0.4 indicate non-polar covalent bonds. Electronegativity differences between 0.4 and 1.7 indicate polar covalent bonds. Polar Covalent Bond- a covalent bond in which the electrons are not shared equally because one atom attracts them more strongly than the other. Non-polar Covalent Bond- a covalent bond in which the electrons are shared equally. Use the periodic table of electronegativities to answer the questions on electronegativity differences.

H 2.1

Li 1.0

Be 1.5 ELECTRONEGATIVITY

(electron attraction!)

B 2.0

C 2.5

N 3.0

O 3.5

F 4.0

Na 0.9

Mg 1.2

Al 1.5

Si 1.8

P 2.1

S 2.5

Cl 3.0

K 0.8

Ca 1.0

Sc 1.3

Ti 1.5

V 1.6

Cr 1.6

Mn 1.5

Fe 1.8

Co 1.9

Ni 1.9

Cu 1.9

Zn 1.6

Ga 1.6

Ge 1.8

As 2.0

Se 2.4

Br 2.8

Rb 0.8

Sr 1.0

Y 1.2

Zr 1.4

Nb 1.6

Mo 1.8

Tc 1.9

Ru 2.2

Rh 2.2

Pd 2.2

Ag 1.9

Cd 1.7

In 1.7

Sn 1.8

Sb 1.9

Te 2.1

I 2.5

Cs 0.7

Ba 0.9

La-Lu 1.0-1.2

Hf 1.3

Ta 1.5

W 1.7

Re 1.9

Os 2.2

Ir 2.2

Pt 2.2

Au 2.4

Hg 1.9

Tl 1.8

Pb 1.9

Bi 1.9

Po 2.0

At 2.2

Fr 0.7

Ra 0.9

Ac 1.1

Th 1.3

Pa 1.4

U 1.4

Np-No 1.4-1.3

Determine the type of bond that would form between the following two elements using differences in electronegativity. Example: Mg – O O is 3.5 and Mg is 1.2, therefore, the difference is 3.5 – 1.2 = 2.3 IONIC Example: Cl – Cl Cl is 3.0. The difference is 3.0 – 3.0 = 0 NON-POLAR COVALENT

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Bond Electronegativity Difference Bond Type

1. C – N

2. Li – F

Bond Electronegativity Difference Bond Type

3. N – Cl

4. Na - Cl

5. O – F

6. B – H

7. Ba – F

8. C – H

Molecular Polarity

Dipole moment- a property of a molecule whereby the charge distribution can be represented by a center of positive charge and a center of negative charge. Polar Molecule- a molecule that has a permanent dipole moment. Determining if a molecule is polar.

1. If ALL of the bonds are non-polar, then the molecule is non-polar.

2. If some or all of the bonds are polar, you can consider the vectors. Vectors are arrows

that point in the direction of the negative charge (the direction the electrons are

pulled). Examples:

O POLAR

H H a. If all the arrows point toward the central atom AND the central atom has lone

pairs, then the atom is polar.

H

NON-POLAR H C H

H

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b. If all the arrows point toward the central atom AND the central atom has no lone

pairs, then the atom is non-polar.

H F POLAR c. If the arrow points toward one atom in a linear molecule, it is polar.

d. If the arrows all point away from the central atom AND there are no lone pairs

on the central atom, then the atom is non-polar.

e. If the arrows all point away from the central atom AND there are lone pairs on

the central atom, then the atom is polar.

3. Another way to determine if a molecular is polar or not, is to look at symmetry.

H NON-POLAR

H C H O C O

H a. If the molecule is symmetrical, then the molecule is non-polar. b.

H

H C H

F

POLAR

H Cl

c. If the molecule is not symmetrical, then the molecule is polar.

d. If the molecule is bent or trigonal pyrimidal, then the molecule is polar (lone

pairs on the central atom mean that it is polar).

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Draw the structural formula for each molecule, and determine if it is polar or non-polar.

Formula Structural Formula Polar/Non-polar

NH3

SCl2

CF4

PCl3

H2S

C2H2

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Bonding and Shape Test Review Determine the formula for the compound formed by the two atoms and indicate if it is an ionic or covalent compound

1. Calcium and Oxygen 2. Nitrogen and Fluorine

3. Sodium and Chlorine 4. Carbon and Oxygen

Draw the dot diagram for each of the IONIC compounds below 5. CaO 6. Na2S 7. SrF2 10. KI Review; http://www.youtube.com/watch?v=9DKId82_rUc Complete the table below.

Formula Electron Dot Diagram

Bonding Orbitals

Shape Structural Formula Polar?

NCl3

CO2

H2O

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VSPER Worksheet:

1) What is the main idea behind VSEPR theory? 2) For each of the following compounds, draw the Lewis diagram, molecular

shapes, and structural diagram for all atoms: a) carbon tetrachloride b) BH3 c) silicon disulfide d) PF3

e) carbon dioxide

f) SF2

CH3F

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Unit 4 Test Review 1. Calcium and Oxygen 2. Carbon and Fluorine

Complete the table below

Draw the Lewis dot diagram for the compounds below 6. AlN 7. HgCl2

8. SCl2 9. NaF 10. BF3 11. SiCl4

Write the formula for the following compounds 12. Aluminum Bromide 13. Dinitrogen Tetroxide 14. Ammonium Fluoride 15. Iron (II) Sulfate 16. Copper (I) Chloride 17. Carbon Dioxide

Formula Electron Dot Diagram Shape Structural Formula Polar?

CH4

H2O

BH3

NH3

CO2