1.3 Chemical Bonding

• Chemistry
• Secondary Education
• Age 12,13

AS Level Chemistry 9701

Topic 3 Chemical Bonding

19 September 2023

Describe how you feel right now 

using an emoji.

😒🙁😐🙂😃

• define electronegativity as the power of an atom to attract electrons to itself
• explain the factors influencing the electronegativities of the elements in terms of nuclear charge, atomic radius, and shielding by inner shells and sub-shells
• state and explain the trends in electronegativity across a period and down a group of the Periodic Table  

I intend to:

19 September 2023, Tuesday

• use the differences in Pauling electronegativity values to predict the formation of ionic and covalent bonds (the presence of covalent character in some ionic compounds will not be assessed) (Pauling electronegativity values will be given where necessary)  
• define ionic bonding as the electrostatic attraction between oppositely charged ions (positively charged cations and negatively charged anions)

I intend to:

19 September 2023, Tuesday

AS Level Chemistry 9701

Topic 3 Chemical Bonding

19 September 2023

• ability of an atom to attract a pair of electrons towards itself in a covalent bond

Electronegativity

19 September 2023, Tuesday

• positive nucleus’s ability to attract the negatively charged electrons, in the outer shells, toward itself

19 September 2023, Tuesday

• used to assign a value of electronegativity for each atom

Pauling Scale

19 September 2023, Tuesday

Which atom is the most electronegative?

• most electronegative atom on the Periodic Table, with a value of 4.0 on the Pauling Scale

Fluorine, F

19 September 2023, Tuesday

• most electronegative atom on the Periodic Table, with a value of 4.0 on the Pauling Scale

Fluorine, F

19 September 2023, Tuesday

What does this tell you?

AS Level Chemistry 9701

Topic 3 Chemical Bonding

19 September 2023

• Nuclear charge
• Atomic radius
• Shielding

Factors affecting electronegativity

19 September 2023, Tuesday

Oxygen

Sulfur

AS Level Chemistry 9701

Topic 3 Chemical Bonding

19 September 2023

Electronegativity trends

19 September 2023, Tuesday

AS Level Chemistry 9701

Topic 3 Chemical Bonding

19 September 2023

• The differences in Pauling electronegativity values can be used to predict whether a bond is covalent or ionic in character.

Predicting bond formation

19 September 2023, Tuesday

• Single covalent bonds are formed by sharing a pair of electrons between two atoms.

Covalent bonds

19 September 2023, Tuesday

• The equal distribution leads to a non-polar molecule.

• When atoms of different electronegativities form a molecule, the shared electrons are NOT equally distributed in the bond.

Polar/Nonpolar bonds

19 September 2023, Tuesday

• The unequal distribution leads to a polar molecule.

• A molecule with partial charges forms as a result

• The more electronegative atom will have a partial negative charge (delta negative, δ-).

• The less electronegative atom will have a partial positive charge (delta positive, δ+).

Polar/Nonpolar bonds

19 September 2023, Tuesday

• If there is a large difference in electronegativity of the two atoms in a molecule, the least electronegative atom’s electron will transfer to the other atom.

Ionic bonds

19 September 2023, Tuesday

• Ionic bond – one atom transfers its electron and the other gains that electron

• The cation – positively charged species that has lost (an) electron(s).
• The anion – negatively charged species that has gained (an) electron(s).

Ionic bonds

19 September 2023, Tuesday

Identify whether the following forms: simple covalent bond, polar bond, nonpolar bond, or ionic bond.

• Sodium chloride
• Bromine gas
• Carbon dioxide gas
• Water molecule

Bonds Practice

19 September 2023, Tuesday

AS Level Chemistry 9701

Topic 3 Chemical Bonding

19 September 2023

• involves the transfer of electrons from a metallic element to a non-metallic element.

Ionic bonding

19 September 2023, Tuesday

• Once the atoms become ions, their electronic configurations are the same as a stable noble gas.
• A potassium ion (K+) has the same electronic configuration as argon: [2,8,8]+
• A chloride ion (Cl-) also has the same electronic configuration as argon: [2,8,8]-

Ionic bonding

19 September 2023, Tuesday

• The ionic bond - electrostatic attraction formed between the oppositely charged ions, which occurs in all directions
• This form of attraction is very strong and requires a lot of energy to overcome

• This causes high melting points in ionic compounds.

Ionic bonding

19 September 2023, Tuesday

• Ions in a lattice are arranged in a regular repeating pattern so that positive charges cancel out negative charges.

• The ions form a lattice structure which is an evenly distributed crystalline structure.

• The final lattice is overall electrically neutral.

Ionic bonding

19 September 2023, Tuesday

AS Level Chemistry 9701

Topic 3 Chemical Bonding

19 September 2023

Draw the dot-and-cross diagrams to show how these ionic compounds formed.

• Sodium chloride
• Magnesium oxide
• Calcium fluoride

Ionic bonding

19 September 2023, Tuesday

Self-Assessment for Learning

T O  D O:

• Identify two ideas you do not understand quite well in our sessions.
• Ask someone who can explain and write the explanations in your notebook.
• Verify your learning from a classmate by sharing it with the teacher.

05 September 2023, Tuesday