NOTES: UNIT 6: Bonding€¦ · compounds contain polyatomic ions have both ionic and covalent bonding. (5.2h) 12/15/2016 1 UNIT 6 BONDING LESSON 6.1 TYPES OF BONDS Objective: By the

Name:

www.mrpalermo.com

Regents Chemistry: Mr. Palermo

NOTES: UNIT 6:

Bonding

Name:

www.mrpalermo.com

Key Ideas

Compounds can be differentiated by their chemical and physical properties. (3.1dd) Two major categories of compounds are ionic and molecular (covalent) compounds.

(5.2g) Chemical bonds are formed when valence electrons are transferred from one atom

to another (ionic), shared between atoms (covalent), mobile within a metal (metallic). (5.2a)

In a multiple covalent bond, more than one pair of electrons are shared between two atoms. (5.2e)

Molecular polarity can be determined by the shape of the molecule and the distribution of charge. Symmetrical (nonpolar) molecules include CO2, CH4, and diatomic elements. Asymmetrical (polar) molecules include HCl, NH3, and H2O. (5.2l)

When an atom gains one or more electrons, it becomes a negative ion and its radius increases. When an atom loses one or more electrons, it becomes a positive ion and its radius decreases. (5.2c)

When a bond is broken, energy is absorbed. When a bond is formed, energy is released. (5.2i)

Atoms attain a stable valence electron configuration by bonding with other atoms. Noble gases have stable valence configurations and tend not to bond. (5.2b)

Physical properties of substances can be explained in terms of chemical bonds and intermolecular forces. These properties include conductivity, malleability, solubility, hardness, melting point, and boiling point. (5.2n)

Electron-dot diagrams (Lewis structures) can represent the valence electron arrangement in elements, compounds, and ions. (5.2d)

Electronegativity indicates how strongly an atom of an element attracts electrons in a chemical bond. Electronegativity values are assigned according to arbitrary scales. (5.2j)

The electronegativity difference between two bonded atoms is used to assess the degree of polarity in a bond. (5.2k)

Metals tend to react with nonmetals to form ionic compounds. Nonmetals tend to react with other nonmetals to form molecular (covalent) compounds. Ionic compounds contain polyatomic ions have both ionic and covalent bonding. (5.2h)

12/15/2016

1

UNIT 6 BONDING

WWW.MRP ALERMO.COM

LESSON 6.1 TYPES OF BONDS

WWW.MRP ALERMO.COM

Objective: By the end of this video you will be able to:

Identify whether a bond is being broken or

formed based upon energy being

absorbed or released

Distinguish between the three types of

bonds and Decide which type of bond is

present based upon the atoms involved

Classify a substance as Ionic, Covalent or

Metallic based upon its properties

What is a Bond?

• Force of attraction between two

atoms

• The energy stored in a bond is

potential energy

Why do atoms Bond?

• Atoms bond together to get a full valence shell of electrons (8) to

become STABLE (Stable Octet)

• Exception: Hydrogen can only have 2 (stable duet)

Forming a Bond

• Energy is RELEASED (EXOTHERMIC) spontaneously

• Forms a STABLE compound

12/15/2016

2

Breaking a Bond

• Energy is ABSORBED (ENDOTHERMIC)

• Stability decreases

• Ex. Ripping two atoms apart requires

ENERGY

Remember BARF

Breaking bonds Absorbs (requires) energy

Release of energy when bonds are

Formed

Check your understanding

Identify whether a bond is being broken or formed based upon energy

being absorbed or released

Three Types of Bonds

1. Ionic

2. Covalent

3. Metallic

Ionic Bonds

• Occur between:

- METALS and NON-METALS

- TRANSFER of ELECTRONS from metal to

nonmetal to form a bond.

Example: sodium reacts with chlorine

electrostatic

attraction

12/15/2016

3

Properties of Ionic Compounds

• Hard

• Crystalline structure

• HIGH Melt/Boiling Pt

• SOLUBLE in water

• Conduct ELECTRICITY

only in solution (aq)

Electrolyte

Compound that separates into ions in

solution and is able to

conduct electricity


Distinguish between the three types of bonds and Decide which type of

bond is present based upon the

atoms involved

Classify a substance as Ionic,

Covalent or Metallic based upon its properties

Covalent Bonds

• Occur between: - NONMETALS and NONMETALS

- SHARING of ELECTRONS to obtain a full valence shell (stable)

- Form MOLECULAR substances

**Trick to remember: SHARING is CARING

Why do they share instead of transfer?

• Each element is not strong enough to remove (“steal”) an electron from the other.

12/15/2016

4

Properties of Covalent Compounds

• Soft

• Low melting and boiling pts (due to

weak attraction between molecules)

• Do not conduct electricity due to

lack of charged particles (ions)

Metallic Bonds

• Between METAL atoms of the SAME element

• Ex. Au atoms in a gold ring

Properties of Metals

• High MP and high BP because bonds are strong.

• Always capable of conducting

electricity because of mobile

electrons (freely flowing delocalized

electrons)

Sea of “mobile” electrons

Example:

What type of bond is created in following:

a. KBr

b. HI

c. NO

d. LiCl




atoms involved



12/15/2016

5

Check your understanding:



atoms involved



You should be able to:

Identify whether a bond is being broken or

formed based upon energy being

absorbed or released

Distinguish between the three types of

bonds and Decide which type of bond is

present based upon the atoms involved

Classify a substance as Ionic, Covalent or

Metallic based upon its properties

LESSON 6.2 BOND POLARITY

WWW.MRP ALERMO.COM


Determine how strongly an atom of an element attracts electrons in a

chemical bond using

electronegativity values from Table S.

Determine the degree of polarity in a

bond based upon the electronegativity difference between

two bonded atoms.

Bond Polarity

• Earth has 2 poles (north & south)

• Magnets also have 2 poles

• Bonds may also have

2 poles (dipole) depending upon

their electronegativities

TYPES OF COVALENT BONDS

12/15/2016

6

Non-polar covalent bond

• Equal sharing of electrons

• Electronegativity difference (E.N.D.)

between atoms 0 - 0.4

• Usually between identical atoms

• Ex. H2

E neg 2.2 E neg 2.2

Polar Covalent Bond

• Unequal sharing of electrons

• E.N.D. between atoms 0.5 – 1.7 (can be

higher than 1.7)

• One atom is slightly negative and one atom is slightly positive.

• This is known as a dipole.

• Ex: HF

Nonpolar

Polar

Ionic

Comparing Ionic and Covalent Bonds How to determine type of bond

Type of Bond

Ionic Bond Covalent Bond

Metal & Nonmetal Non metal & non metal

Non polar covalent Polar covalent

E.N.D. > 0.4 E.N.D. ≤ 0.4

Summary of Bond Types

0.0 0.4 1.7-2.0

Covalent Ionic

Nonpolar Polar

Example: Ionic, Polar or NP

• Na-S

• C-Br

• C-C

• H-O

• F-F

• K-O

12/15/2016

7



chemical bond using




two bonded atoms.



chemical bond using




two bonded atoms.

LESSON 6.3 LEWIS DIAGRAMS FOR IONIC COMPOUNDS

WWW.MRP ALERMO.COM


Construct Lewis dot diagrams for ionic compounds

Lewis Dot Diagram: Ionic Compounds

• Draw ion dot diagrams next to each

other making sure that:

- The ion charges cancel out (add up to

zero)

- The opposite charged ions are next to

each other, and the like charged ions

are as far away from each other as they

can be.

Recall

• Dot diagrams for positive ions (metals)

• Dot diagrams for negative ions

(nonmetals)

x

12/15/2016

8

Example:

Dot diagram of NaCl

Dot diagram of CaCl2

Example: Barium Sulfide

Example: Aluminum Oxide


Can you construct Lewis dot diagrams for ionic compounds


Construct Lewis dot diagrams for ionic compounds

LESSON 6.4 LEWIS DIAGRAMS FOR COVALENT COMPOUNDS

WWW.MRP ALERMO.COM

12/15/2016

9


Construct lewis dot diagrams for covalent compounds

Determine the number of electrons

shared in a covalent bond

Lewis Dot diagrams: Covalent Compounds

1. Write the element symbols next to each other (if more than two symbols write the UNIQUE symbol in the center)

2. Count up the total number of valence electrons for all the elements

3. Put 8 electrons around the central atom (if only two atoms pick one to place them around)

4. Distribute the remaining valence electrons

to the other atoms equally until you run out

5. Check to see if each atom has a complete

valence shell (8 electrons except Hydrogen

which has 2)

Cl Cl

**A shared pair of electrons counts for both

atoms **Each atom of Fluorine now has 8 electrons.

Total # of valence electrons for 2 chlorine atoms 7 x 2 = 14

Example H2O:

Total # of valence electrons for H2O = 2(1) + 6 = 8

Example F2:

Total # of valence electrons for F2 = 7 + 7= 14

Example: Draw dot diagram for HBr

12/15/2016

10



6. If all atoms do not have a full valence shell then you must ADD

MULTIPLE BONDS (sharing of 2 or more

PAIRS of electrons)

Example: CO2

How many electrons can be shared?

• Single bond = sharing a pair (2) electrons

• Double bond = sharing 2 pair (4)

electrons

• Triple bond = sharing 3 pair (6) electrons

Example: Draw the dot diagram for O2

Stop and Think:

Draw the dot diagram for N2





12/15/2016

11





LESSON 6.5 MOLECULAR POLARITY

WWW.MRP ALERMO.COM


Determine the polarity of a molecule

Determine the shape of a molecule

Types of electron pairs

• Bonding pairs - form bonds

• Lone pairs - nonbonding e-

Molecular Polarity depends on:

1. Bond Polarity

2. Shape of molecule (Symmetrical vs.

nonsymmetrical)

Shape caused by: VSEPR

• The Valence Shell Electron Pair

Repulsion

• Valence electrons are arranged as

far from one another as possible to minimize the repulsion between them

(Like charges repel each other)

12/15/2016

12

Polar Molecules

• A molecule is polar if it:

- Contains POLAR BONDS

- Is ASYMMETRICAL (not symmetrical)

****If there are LONE PAIRS on central

atom then the molecule is automatically POLAR

Non Polar Molecules

• A molecule is nonpolar if it:

- Contains only NONPOLAR BONDS

- Is SYMMETRICAL

SHAPES OF POLAR MOLECULES

1. LINEAR

• Must be asymmetrical

δ+ δ-

2. BENT

• 2 pair of lone pair electrons on central atom

δ-

δ+ δ+

3. PYRAMIDAL

• 1 lone pair of electrons on central atom

δ+

δ+

δ+

δ-

12/15/2016

13




SHAPES OF NONPOLAR MOLECULES

1. LINEAR

• Must be SYMMETRICAL

δ+ δ+ δ- δ+ δ-

2. TETRAHEDRAL

• Central atom bonded to 4 identical atoms

Summary of Shapes and Polarity

1 or 2 bonds only linear Polar if asymmetrical

Nonpolar if symmetrical

2 bonded pairs and 2 lone

pairs

bent polar


pair

pyramidal polar


pairs

tetrahedral Non-polar

If the central atom has ... the shape is Bond type

Example: Determine the molecular polarity and shape of CCl4

• Nonpolar because its symmetrical

• Tetrahedral

12/15/2016

14

Example: Determine the molecular polarity and shape of H2S

• Polar due to 2 pair of lone pair e-

• Bent







LESSON 6.6

INTERMOLECULAR FORCES

WWW.MRP ALERMO.COM


Determine the type of intermolecular force that exists between covalent

compounds

Determine the effect of

intermolecular forces on melting and

boiling point

WHAT TYPE OF FORCES HOLD MOLECULES TOGETHER?

12/15/2016

15

Intermolecular Forces (IMF’s)

• Weak forces of attraction BETWEEN molecules (covalent compounds)

Types of Intermolecular Forces

1. Dispersion Forces

2. Dipole-Dipole

3. Hydrogen Bonding

Dispersion Forces

• Weakest IMF

• Occurs between nonpolar

molecules

• Explains how nonpolar molecules

can exist in solid & liquid phase

• MORE ELECTRONS = GREATER

FORCE

Example: H2

Dipole-Dipole

• Between polar covalent molecules

• Partial negative end of dipole attracted

to partial positive end of another dipole

• The more polar the bond the greater

the IMF between the molecules

12/15/2016

16

Example: HCl Hydrogen Bonding

• Special case of dipole interaction.

• Strongest IMF

• Occurs between hydrogen of 1

molecule and F, O or N in another

• Remember

“H bonding is FON”

Example: NH3 Practice: What type of IMF occurs

between molecules of Cl2

• Dispersion force because Cl2 is nonpolar



compounds

Recall

• The stronger the intermolecular force the greater the melting and boiling

point of a substance

12/15/2016

17

Example at STP

H2 (g) H2O (l)


Determine the effect of intermolecular forces on melting and

boiling point



compounds

Determine the effect of

intermolecular forces on melting and

boiling point

Documents

NOTES: UNIT 6: Bonding€¦ · compounds contain polyatomic ions have both ionic and covalent bonding. (5.2h) 12/15/2016 1 UNIT 6 BONDING LESSON 6.1 TYPES OF BONDS Objective: By the