Bonding 3.1.3

Question 1

Dative covalent bond

Answer 1

Formed when an atom uses a lone pair of electrons to form a covalent bond
Once formed, it is not different from any other bond

Question 2

Graphite vs diamond

Answer 2

⋆GRAPHITE has weak intermolecular forces between layers; DIAMOND has no layers
⋆GRAPHITE has 3 bonds per Carbon; DIAMOND has 4 bonds per Carbon
⋆ GRAPHITE has 1 delocalised electron per Carbon; DIAMOND has no delocalised electrons
⭒both are carbon only
⭒both have covalent bonds

Question 3

How to predict bonding based off electronegativity

Answer 3

both <1.6-1.9 → metallic

either > 1.4 AND difference <0.5 →covalent

either >1.9 AND difference 0.5-2.1 →polar covalent

difference >2.1 ionic

Question 4

Electronegativity of Carbon

Answer 4

2.5

Question 5

Electronegativity of nitrogen

Answer 5

3.0

Question 6

Electronegativity of oxygen

Answer 6

3.5

Question 7

Electronegativity of flourine

Answer 7

4.0

Question 8

Electronegativity of chlorine

Answer 8

3.0

Question 9

What is empirical formula

Answer 9

The ratio of ions in an ionic formula

Question 10

Physical properties of ionic compounds

Answer 10

High melting point
Hard
Brittle
Can conduct electricity when molten

Question 11

Why do ionic compounds have high melting points

Answer 11

strong electrostatic forces of attraction between oppositely charged ions that require a lot of energy to overcome

Question 12

Why are ionic compounds hard

Answer 12

Lattice of many electrostatic forces of attraction that require lots of energy

Question 13

why are ionic compounds brittle

Answer 13

mixed sizes of ions so it is hard for them to slide over each other

Question 14

how can ionic compounds conduct electricity when molten/dissolved but not when solid

Answer 14

in liquid, the charged ions are free to move around the lattice

Question 15

How can ionic compounds dissolve in water

Answer 15

water molecules are polar so attract the charged ions in the lattice via ion-dipole forces pulling them away from the lattice dissolving the structure

Question 16

What is electronegativity

Answer 16

The power of an atom to attract negative charge towards itself within a covalent bond
This depends on size, nuclear charge
Increases along a period as atomic radius decreases
Decreases down a group as shielding increases

Question 17

Factors affecting electronegativity

Answer 17

Atomic radius→ Smaller atoms are more electronegative because their electrons are closer to the nucleus resulting in stronger electrostatic attraction
Nuclear charge → A higher positive charge in the nucleus increases the strength of the electrostatic attraction between the nucleus and the electrons, making the atom more electronegative
Shielding → Electrons in inner shells can weaken the electrostatic attraction between the nucleus and the outer shell electrons, reducing and atoms electronegativity

Question 18

How does atomic radius affect electronegativity

Answer 18

ELECTRONEGATIVITY DECREASES AS A.R INCREASES
Smaller atoms are more electronegative because their electrons are closer to the nucleus resulting in stronger electrostatic attraction

Question 19

How does nuclear charge affect electronegativity

Answer 19

ELECTRONEGATIVITY INCREASES AS NUCLEAR CHARGE INCREASES
A higher positive charge in the nucleus increases the strength of the electrostatic attraction between the nucleus and the electrons, making the atom more electronegative

Question 20

How does Shielding affect electronegativity

Answer 20

ELECTRONEGATIVITY DECREASES AS SHIELDING INCREASES
Electrons in inner shells can weaken the electrostatic attraction between the nucleus and the outer shell electrons, reducing and atoms electronegativity

Question 21

EXAM QUESTION:
Bonding in ice
Boiling point of water vs methane

Answer 21

H
H - :O: - H :O:
H
★Tetrahedral representation with covalent and H bonds
★2 H bonds per molecule
★Both methane and water contain strong covalent bonds that are not broken on boiling
★ H-bonds in water are stronger than the VDW forces in methane
★ so less energy is required to break the forces between methane molecules

Question 22

Heteronuclear diatomic molecule

Answer 22

Electron density may be focused towards one atom creating a dipole
It is a polar molecule because the electron density lies towards the electronegative element

Question 23

Electronegativity across a period

Answer 23

Electronegativity increases across a period
★the atomic radius decreases and nuclear charge increases (more protons in nuc and more electrons in shells) so there is stronger electrostatic attraction between the nucleus and electrons in the outer shell

Question 24

Electronegativity down a group

Answer 24

ELECTRONEGATIVITY DECREASES DOWN A GROUP
although nuclear charge increases, atomic radius increases more significantly
Shielding also increases significantly
The increases distance between nucleus and outer electrons combines with greater shielding weakens electrostatic attraction between them so electronegativity decreases

Question 25

How do polar bonds arise?

Answer 25

FROM SIGNIFICANT ELECTRONEGATIVITY DIFFERENCES

Question 26

Van der Waals forces between molecules

Answer 26

Electron density can be anywhere at any given time. In some cases, electron density can be located mainly on one side of the molecule creating a temporary dipole. If two molecules are in close proximity, a temporary dipole can be induced.

Question 27

Intermolecular bond types and their relative strengths

Answer 27

Ionic and covalent -1000 Hydrogen- 50 Dipole-dipole -10 Van der waals' -1

Question 28

Hydrogen bonding

Answer 28

When an H atom is bonded to a very electronegative atom (only F,N,O) to produce a polar bond The delta positive H atom is then attracted towards the lone pair of electrons from an atom in another molecule

Question 29

Why does ice float

Answer 29

Hydrogen bonds are constantly breaking and reforming Stable H bonds hold molecules apart so it is less dense than water.

Question 30

Linear shape

Answer 30

Cl-Be-Cl 2 electron pairs

Question 31

Trigonal planar

Answer 31

BF3 3 electron pairs Bond Angle: 120

Question 32

Tetrahedral

Answer 32

Methane, CH4 4 electron pairs Bond angle: 109.5

Question 33

Trigonal Bipyramidal

Answer 33

PCl4 5 electron pairs Bond angles: 120, 90

Question 34

Octahedral

Answer 34

SF6 6 electron pairs Bond angle: 90

Question 35

Lone pairs

Answer 35

Have more repulsion than bond pairs so increase angle by 2.5