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6 – Electronegativity. Leaving Certificate Chemistry. By the end of today’s class you should be able to :. Define electronegativity Tell what the trend is as you go across a group Tell what the trend is as you go down a group Be able to explain these trends. Electronegativity. 2008

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6 – Electronegativity

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6 electronegativity

6 – Electronegativity

Leaving Certificate Chemistry


By the end of today s class you should be able to

By the end of today’s class you should be able to :

  • Define electronegativity

  • Tell what the trend is as you go across a group

  • Tell what the trend is as you go down a group

  • Be able to explain these trends


Electronegativity

Electronegativity

2008

Q5 (a) (5)

2006

Q5 (a) (6)

2005

Q5 (a) (6)

2003

Q5 (a) (6)


Electronegativity table page 46 mt

Electronegativity Table (Page 46 – MT)


Learning objectives

Learning objectives

  • What the trend going across any period in the Periodic table is and an explanation of this

  • What the trend going down any group in the table is and an explanation of this


6 electronegativity

Going across period 1

Lithium

Berylium

Boron

Carbon

3

4

6

5

What happens to the number of shells filled?

What happens to the nuclear charge?

What happens to the size of the atom?


Values increase across any period

Values Increase across any Period

Lithium

Beryllium

Boron

Carbon

Nitrogen

1. Nuclear charge is increasing

2. Atomic radii are decreasing

2006

Q5 (b) (6)


6 electronegativity

3

Going down group 1

What happens to the size of the atom (atomic radius)?

What happens to the size of the nuclear charge?

What happens to the number of shells filled?

11

19


Values decrease down any group

Values decrease down any Group

  • Increasing Nuclear charge BUT the effect (on the outermost electron) is offset by an inner electron screening effect

Lithium

11

Sodium

2. Atomic Radii are increasing as you go down any group

Potassium

19

2008

Q5 (b) (9)


Learning objectives1

Learning objectives

  • Know the rules for predicting bonding type between atoms

  • Be able to use these rules to correctly predict bonding type used.


Predicting the bond type

Predicting the bond type

Electronegativity Values can be used to predict the bond type of molecules in a chemical bond

With 2 Bonding Atoms

2008

Q5 (c) (9)

Difference in electronegativity

0

2007

Q5 (b) (6)

Bond is Non-polar (pure Covalent)

Greater

than 1.7

Between 0.4 - 1.7

Between 0 - 0.4

Bond is Ionic

Bond is weakly polar

Bond is Polar (Covalent)

(Covalent)


Use electronegativity values to predict the type of bonding in iodine i 2

Use electronegativity values to predict the type of bonding in iodine (I2)

iodine (EV) = 2.7

Iodine (EV) = 2.7

Difference in EV = 0

Iodine is a non-polar (Covalent) molecule


Use electronegativity values to predict the type of bonding in water

Use electronegativity values to predict the type of bonding in water

Oxygen (EV) = 3.5

Hydrogen (EV) = 2.1

Difference in EV = 1.4

Water is a polar (Covalent) molecule


Use electronegativity values to predict the type of bonding in methane

Use electronegativity values to predict the type of bonding in methane

Carbon (EV) = 2.5

Hydrogen (EV) = 2.1

Difference in EV = 0.4

Methane is a slightly weakly polar (Covalent) molecule


Use electronegativity values to predict the type of bonding in magnesium chloride

Use electronegativity values to predict the type of bonding in magnesium chloride

Magnesium (EV) = 1.2

Chlorine (EV) = 3.0

Difference in EV = 1.8

Mg

Cl

Magnesium chloride is an ionic molecule

2

1

MgCl2


Use electronegativity values to predict the type of bonding in hydrogen sulfide

Use electronegativity values to predict the type of bonding in hydrogen sulfide

Hydrogen EV) = 2.1

Sulfur (EV) = 2.5

Difference in EV = 0.4

H

S

Hydrogen sulfide is a slightly weakly polar (Covalent) molecule

1

2

H2S


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