1.4 Bonding

Question 1

What is a chemical bond?

Answer 1

A force that holds together two or more atoms, ions, molecules or any combination of those.

Question 2

What is ionic bonding?

Answer 2

Strong electrostatic forces of attraction between positive and negative ions. Bonding between metal and non-metal. (metal gives electron, non-metal receives electron so both atoms achieve full outershell)

Question 3

What is covalent bonding?

Answer 3

Bonding between non-metal and non-metal only. (atoms join together to share electrons to achieve a full outershell)
There are no charges in covalent bonding

Question 4

What is metallic bonding?

Answer 4

Bonding between positive ions and a sea of electrons.

Question 5

What are the typical properties of metals?

Answer 5

Conduct electricity
Conduct heat
High melting points
Malleable (can be bent into shapes)
Ductile (can be drawn into wires)

Question 6

What are the typical properties of non-metals?

Answer 6

Don't conduct electricity
Don't conduct heat
Low melting points
Not malleable
Not ductile

Question 7

What is an ionic crystal?

Answer 7

A giant lattice (structure) held by electrostatic attraction of oppositely charged ions.

Question 8

Why do ionic compounds have a high melting point?

Answer 8

Ionic compounds have strong electrostatic attration of oppositely charged ions. Therefore it requires a lot of energy to break the ionic bonds.

Question 9

Where are the attractive forces in ionic bonding of two atoms?

Answer 9

Between oppositely charged ions

Between outer electron and nucleus of different ions

Question 10

Where are the repulsive forces in ionic bonding of two atoms?

Answer 10

Between outer electron and outer electron (same charge, both -)

Between 2 nuclei

Between 2 same charged ions

Question 11

Where are the attractive forces in covalent bonding of two atoms?

Answer 11

Between outer electron and linear nucleus

Question 12

Where are the repulsive forces in covalent bonding of two atoms?

Answer 12

Between outer electron and outer electron

Between inner nucleus and inner nucleus

Question 13

What are covalent compounds made of?

Answer 13

Simple molecules with WEAK forces between them but the covalent bonds are STRONG

Question 14

What does the term ‘diatomic’ mean?

Answer 14

molecule consists of two same atoms.

Question 15

What are the diatomic elements?

Answer 15

H₂, N₂, F₂, O₂, I₂, Cl₂, Br₂

Question 16

What is coordinate/dative bonding?

Answer 16

A type of covalent bonding where both or more electrons in the bond are supplied by the same atom

e.g BF₃ (Boron fluoride)
NH₃ (Ammonia)

Question 17

What does electronegativity mean?

Answer 17

The ability of an atom in a covalent bond to attract a shared pair of electrons

Question 18

What’s the trend on electronegativity?

Answer 18

electronegativity increases from left to right across a period (increases up a group in a same period) in the periodic table and decreases down a group from group 7
electronegativity also decreases down the periods.

Question 19

which atom has the greatest electronegativity?

Answer 19

Fluorine

Question 20

Which atom has the least electronegativity?

Answer 20

Francium

Question 21

Why the electronegativity of a fluorine atom is greater than oxygen atom?

Answer 21

Because fluorine has more protons than oxygen therefore it got a greater nucleus charge so it can attract electrons easier

Question 22

Why the electronegativity of a fluorine atom is greater than chlorine atom?

Answer 22

Because chlorine is further down in the group than fluorine therefore it has a more filled electron shells. This means that there is more shielding of the nucleus and therefore the pull of nucleus to attract electrons is less.

Question 23

What are the six most electronegative elements?

Answer 23

Fluorine, oxygen, nitrogen, chlorine, bromine and sulfur

Question 24

What can be used to represent the charge on the electronegative atoms?

Answer 24

𝛿⁻ (delta minus)

Question 25

What can be used to represent the atoms that are bonded to electronegative atoms?

Answer 25

𝛿⁺ (delta plus)

Question 26

What are dipoles?

Answer 26

dipoles are formed when a covalent bond exists between atoms of differing electronegativity. The shared pair of electrons is displaced towards the more electronegative atom.

Question 27

What is a polar molecule?

Answer 27

A molecule in which one end of the molecule is slightly positive, while the other end is slightly negative.

Question 28

How are polar molecules formed?

Answer 28

The displacement of electron density makes the less electronegative atom slightly electron deficient (loss of electrons, 𝛿⁺) while the more electronegative atom has a slight excess of electron density (𝛿⁻) This charge separation creates an electric dipole.

Question 29

What does polarity means?

Answer 29

Unequal sharing of electrons

Question 30

Is carbon - hydrogen a polar bond?

Answer 30

NO, because the electronegativity of carbon and hydrogen are so similar that THEY ARE NOT considered as a polar covalent bond . SO NEVER PUT 𝛿⁻ OR 𝛿⁺ on a C-H bond!!!!!

Question 31

Why polar molecules have a high melting point?

Answer 31

They have attraction between opposite charges therefore are harder to pull apart, so a lot energy are needed to break the polar covalent bond.

Question 32

What are the melting points dependent on in covalent bonds?

Answer 32

how strong the forces between molecules. If the force is weak, it's easier to pull apart therefore less energy are needed to break the bond (low melting point). If the force is strong, it's harder to pull apart therefore more energy are needed to break the bond (high melting point)

Question 33

What does polar bond arise means?

Answer 33

When the electrons are not shared equality in a covalent bond. One of the atom exerts a stronger attractive force on the electrons than the other atom

Question 34

Explain why hydrogen fluoride is classed as a polar molecule and describe how this polarity arises?

Answer 34

Hydrogen atom has a low electronegativity compared to fluorine atom therefore the charge separation causes the hydrogen fluoride to become a polar molecule. In the H-F bond, fluorine has the greater electronegativity therefore it pulls the shared pair of electrons more towards itself, causing unequal shared pair of electrons

Question 35

Why water has a high boiling temperature of 100°C?

Answer 35

Oxygen atom is more electronegative than hydrogen atoms therefore it has the ability to pull electrons more towards itself. causing one end of the molecule slightly positive and the other end of the molecule slightly negative. The electrostatic attraction between negative and positive charges is strong as well as a great hydrogen bonds between water molecules therefore stronger intermolecular forces within the structure therefore a lot energy are needed to break the hydrogen bonds therefore it has a high boiling point.