IQ4

Question 1

Electronegativity and Bonding.

Answer 1

To determine the type of bond, you need to figure out the difference in electronegativity.

Question 2

Ionic bonding

Answer 2

Bonding that involves the movement fo electrons from one atom to another to achieve stable noble gas configuration.
Involves metal and nonmetal
Results in anions and cations
Being held together by strong electrostatic forces in 3d crystal lattice. Chemical formula represents the empirical formula of the compound.

Question 3

Property of an ionic compound: High melting point

Answer 3

Due to strong electrostatic forces of attraction between a cation and anion.

Question 4

Property of an ionic compound: Non-conductor of electricity in solid state

Answer 4

Oppositely charged particles being in fixed positions.

Question 5

Property of an ionic compound: conductivity of electricity in liquid state.

Answer 5

Due to ions being able to move freely in the liquid. (It has to be in liquid form)

Question 6

Property of an ionic compound: Hard

Answer 6

Electrostatic attraction between oppositely charged particles

Question 7

Property of an ionic compound: Brittle

Answer 7

Oppositely charged particles at fixed locations. Displacement of ions move then closer to ions of similar charge which increases repulsive forces causing further fracture

Question 8

Covalent bonding

Answer 8

Chemical bonding which involves sharing electrons between atom to get noble gas electron configuration.
Involves non-metal atoms
Each pair of shared electrons is called covalent. Forms strong covalent bonds. Either polar or non polar.

Question 9

Covalent molecular

Answer 9

Strong covalent bonds between atoms. Weak intermolecular forces holding molecules together.

Question 10

Covalent molecular properties

Answer 10

Melting and boiling points:
Low due to weak attraction forces between molecules.
Electrical conductivity: Lack of molecule charged species of delocalised electrons.
Hardness: Soft due to weak forces existing between molecules

Question 11

Covalent network

Answer 11

Covalent bonding lattice that extends indefinitely throughout the crystal.
E.g Diamond is the strongest structure because of covalent network.
Graphite is the exception because it has delocalised electrons.

Question 12

Covalent network properties

Answer 12

Melting/boiling point: Due to strong covalent bonding. 3d rigid structure
Electrical conductivity: Due to lack of mobile charge species of delocalised electrons.
Hardness: Due to strong covalent bonding, which forms 3d structure.

Question 13

Polarity of covalent bonds and molecules.

Answer 13

When sharing of electrons is not equal. When they have a difference of electronegativity scales between 0.4-1.8
Electrons stay closer to the more electronegative atom.

Question 14

Polarity in hydrogen fluoride

Answer 14

Difference in electronegativity is 1.78. The shared electrons will stay closer to fluorine. Hydrogen atom will become slightly positive.

Question 15

Polarity of molecules

Answer 15

Depends on two factors: Polarity of bonds, the shape of the molecule.

Question 16

Molecule shape

Answer 16

arrange themselves spatially to get as far away from each other as possible. Determines the shape of the molecule. Valence electron of central atom can be two types: Bonded pairs, lone pair.
Depending on the type of electron the amount of repulsion differs .

Question 17

VSEPR theory

Answer 17

1. Lone pair to lone pair repulsion is strongest.
2. Lone pair to bonding pair repulsion is intermediate.
3. Bonding pair to bonding pair repulsion is weakest.
   Lone pair to lone pair is why water is always less than 109.5

Question 18

Shapes and angles for vsepr theory

Answer 18

Question 19

Polarity of molecules

Answer 19

When the molecule is asymmetrical. Consider electronegativity differences.

Question 20

Metallic Bonding

Answer 20

Bonding in metals is three dimensional lattice of positive ions in a sea of delocalised electrons.
The weaker the hold of the electrons by the nucleus the higher its metallic character and the better the thermal and electrical conductivity.

Question 21

Properties of metallic bonding

Answer 21

High melting points: Strong attraction between positively charged metal ions and delocalised electrons.
Good heat and electricity conductors:
High mobility of delocalised electrons
Malleable and ductile: Delocalised electrons not belonging to a particular metal atom. ONe layer of ions can slide over another. Electrons and ions can rearrange.
Hardness: Due to tightly packed atoms.

Question 22

Allotropy

Answer 22

Allotropes are different forms of the same elements.
Different bonding arrangement between atoms in different structure with different physical properties

Question 23

Allotropes of carbon

Answer 23

Diamond, graphite

Question 24

Allotropes of Oxygen

Answer 24

Biomolecule
Ozone layer (3 oxygens)

Question 25

Strength of Intermolecular forces

Answer 25

Increasing strength: Dispersion Dipole-Dipole Hydrogen Boning

Question 26

Dispersion forces

Answer 26

Sometimes referred to as Van der waals force of attraction. Between molecules of all covalent substances and non metal atoms. In non-polar compounds, dispersion forces are the only type of intermolecular force present.

Question 27

Dipole-Dipole Forces

Answer 27

Involves interaction polar molecules such as nitrogen and oxygen. The negative end of one dipole attracts the positive end of the neighbouring dipole. They are stronger than dispersion forces. Polar molecules have both dispersion and dipole-dipole forces.

Question 28

Dipole-Dipole effect on bp/Mp

Answer 28

Dipole-Dipole forces are stronger forces to overcome and hence usually have a higher melting and boiling point.

Question 29

Hydrogen bonding

Answer 29

Electrostatic attraction (Positive and negative)(only polar molecules) between a hydrogen atom and an electronegative atom. Strongest of all bonding. Goes from the Hydrogen atom to the lone electron pair from the other molecule.