Bonding and Structure

Question 1

Ionic Bond Definiton

Answer 1

Strong electrostatic forces of attraction between oppositely charged ions

Question 2

Physical Properties of Ionic Compounds

Answer 2

High Melting/Boiling Points
- They have a giant ionic lattice structure
- There are many strong electrostatic forces of attraction between oppositely charged ions

Question 3

Factors affecting the strength of ionic bonds

Answer 3

Greater ion charge = Stronger Ionic Bond
Smalle ionic radius = Stronger Ionic Bond
Smaller = More attractive

Question 4

Electrical Conductivity

Answer 4

Ionic Compounds WILL NOT conduct electricity in the SOLID state as ions are in a fixed lattice position which means no mobile charged carriers (ions,atoms etc)
They WILL conduct electricity in the molten/aqueous state as the ions are free to move

Question 5

Solubility

Answer 5

Ionic compounds WILL dissolve in water as the ions make attractions to the different atoms in water and are ‘pulled apart’

Question 6

Covalent Bond (2 non metals) Definition

Answer 6

A covalent bond is a shared pair of electrons between atoms

Question 7

Coordinate/dative covalent bonding

Answer 7

When one atom provides both the electrons needed to form a covalent bond
- Atom donating needs to have a lone pair
- Atom receiving needs to have a vacant orbital
- Bond represented with an arrow

Question 8

Molecular geometry

Answer 8

2bprs, 0lprs - 180° - Linear
3bprs, 0lprs - 120° - Trigonal Planar
4bprs, 0lprs - 109.5° - Tetrahedral
3bprs, 1lpr - 107° - Trigonal Pyramid
2bprs, 2lprs - 104.5° - Non-Linear
6bprs, 0lprs - 90° - Octahedral

Question 9

Repulsion

Answer 9

LP-LP repulsion>BP-LP repulsion>BP-BP
each lone pair reduces the bond angle by 2.5°

Question 10

Electronegativity Defintion

Answer 10

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

Question 11

Increased electronegativity

Answer 11

Number of protons increase
Atomic radius decreased
If going up then shielding decreased

Question 12

Polar Bond

Answer 12

||||| A covalent bond in which there is an unequal share if the electrons due to differing electronegativity |||||
(the electron density is distributed unequally)
If the difference in electronegativity is greater that 0.4 the bond will be polar

Question 13

Electron density

Answer 13

Delta Negative will be the bigger side
Delta Positive is the smaller side
Opposite sides create a dipole

Question 14

Symmetry/Polarity

Answer 14

Some molecules have polar bonds but they are not polar molecules because they are symmetrical and the dipoles cancel out
C-H bonds are non polar

Question 15

Intermolecular Forces
(

Answer 15

Covalent bonding leads to the formation of giant or simple molecules
Most Covalent compounds are simple molecules eg water
Intermolecular forces are weaker that the covalent bonds between the atoms within the molecule

Question 16

3 Intermolecular Forces

Answer 16

Weakest : Induced Dipole-Dipole forces between molecules
Middle : Permanent Dipole-Dipole forces between molecules
Strongest : Hydrogen Bonding between molecules

Question 17

Temporary Dipole

Answer 17

Electrons constantly moving so the charge can change distribution at any time - one side of a molecule can be more negative than another because the electrons moved closer to that side

Question 18

Induced Dipole-Dipole/London Forces
(In all simple molecules)

Answer 18

A temporary dipole in one molecule induces a dipole in another molecule
Attraction between delta positive on one molecule and delta negative on an adjacent molecule
This is called induced dipole dipole intermolecular forces

Question 19

Factors affecting the strength of IDDs

Answer 19

Size/Mr of the molecule - bigger molecule = more electrons = stronger attraction = more IDD forces between molecules
S.A Contact - more S.A contact = more IDD forces between molecules
Larger molecule = Stronger IMFs = higher melting/boiling point

Question 20

Permanent Dipole-Dipole Forces between polar molecules

Answer 20

• This type of force occurs between molecules which are polar
• A polar bond is where there is a difference in electronegativity between the atoms
• There is an attraction between a delta positive on one molecule and a delta negative on another adjacent molecule

Question 21

Hydrogen Binding between molecules

Answer 21

Only occurs between polar molecules which have a hydrogen bond directly bonded to O,N or F
O,N,F are the most electronegative atoms
Big difference in electronegativity between negativity between H and the O,N,F
So the O,N,F will pull the pair of electrons in the bond very strongly towards themselves
So the hydrogen nucleus is very delta positive
A lone pair of electrons in a neighbouring molecule containing O,N,F is attracted to the hydrogen

Question 22

Features of a Hydrogen Bonding Diagram

Answer 22

Hydrogen bond clearly show between the lone pair and the delta positive Hydrogen on the other molecule
Partial Charges in all atoms
All lone pairs shown clearly

Question 23

The anomalous properties of water
Explaining why water has a relatively high melting/boiling point

Answer 23

Hydrides of Group 4 elements : As the Mr(size) increases, the boiling point increases
Overall trend due to the increasing strength of IDDs

Hydrides of Group 6 elements :
anomaly (H20) which is really high due to the presence of hydrogen bonds
rest increase due to increasing strength of IDDs Hydrides

Question 24

Physical properties of Simple Molecular structures

Answer 24

Low melting/boiling points
-Weak IMFs between molecules which require little energy to overcome

Electrical Conductivity
WONT conduct electricity in solid/molten state because there are no charged particles free to move (no mobile charged carries)

Solubility
Non-polar molecules WONT generally dissolve in water because they can’t form hydrogen bonds