Bonding & Structure

Question 1

What does it mean if there is a large difference in electronegativity between 2 elements

Answer 1

• the movement of bonding e- from the element of lower electronegativity to the element of higher electronegativity is complete
• results in formation of ions

Question 2

ionic compounds form between

Answer 2

Metals and non-metals

Question 3

What are ionic bonds

Answer 3

The electrostatic attraction between positive and negative ions

Question 4

What do ionic compounds form

Answer 4

Lattice structures of oppositely charged ions

Question 5

What are covalent bonds

Answer 5

A shared pair of electrons between atoms

Question 6

What is the covalent bond a result of

Answer 6

2 positive nuclei being held together by their common attraction for the shared pair of electrons

Question 7

What do pure covalent bonds form between

Answer 7

Atoms of identical electronegativity

Question 8

When do polar covalent bonds form

Answer 8

When the atoms attraction for the pair of bonding e- are different

Question 9

What does δ- indicate

Answer 9

The partial negative charge of an atom which causes a dipole

Question 10

What does δ+ indicate

Answer 10

The partial positive charge of an atom which causes a dipole

Question 11

What does the difference in electronegativities between bonded atoms show

Answer 11

Gives an indication of the ionic character

Question 12

The larger the difference in electronegativities…

Answer 12

• the more polar the bond will be

- greater ionic character

Question 13

What can we use to deduce the type of bonding and structure in the compound

Answer 13

Physical properties e.g. state at room temp, MP/BP, solubility and electrical conductivity.

Question 14

What are Van der Waals forces

Answer 14

Intermolecular forces acting between molecules

Question 15

What are the different types of Van der Waals forces

Answer 15

• London dispersion forces

- permanent dipole - permanent dipole interactions (includes hydrogen bonding)

Question 16

What are london dispersion forces

Answer 16

Forces of attraction that can operate between ALL atoms and molecules

Question 17

What is the strength of london dispersion forces

Answer 17

Weaker than all other types of bonding

Question 18

Why do london dispersion forces form

Answer 18

As a result of electrostatic attraction between temporary and induced dipoles

Question 19

What is the strength of london dispersion forces related to

Answer 19

The number of electrons within an atom or molecule

Question 20

What is a polar molecule

Answer 20

It has a permanent dipole

Question 21

What else can make a molecule polar

Answer 21

The spatial arrangement of polar covalent bonds (3D symmetry)

Question 22

What are permanent dipole - permanent dipole interactions

Answer 22

Additional electrostatic forces of attraction between polar molecules

Question 23

What is the strength of permanent dipole - permanent dipole interactions compared to LDFS

Answer 23

Permanent dipole-permanent pole interactions are stronger than London dispersion forces

Question 24

What is a hydrogen bond

Answer 24

Electrostatic forces of attraction between molecules that contain these highly polar bonds

Question 25

What do highly polar bonds consist of

Answer 25

A hydrogen atom bonded to an atom of a strongly electronegative element (such as fluorine, oxygen or nitrogen)

Question 26

Strength of hydrogen bonds

Answer 26

- Stronger than permanent dipole - permanent dipole interactions - weaker than a covalent bond

Question 27

How do we make predictions about the strength of the intermolecular forces

Answer 27

By considering the polarity and number of electrons present in molecules

Question 28

The MP & BPs of polar substances are ...

Answer 28

Higher than the MP & BPs of non-polar substances

Question 29

What properties of substances are affected by hydrogen bonding

Answer 29

- boiling point - melting point - viscosity - solubility in water

Question 30

What are the irregular boiling points of ammonia, water and hydrogen fluoride a result of

Answer 30

Hydrogen bonding

Question 31

What causes the density of ice to be less than water at low temperatures

Answer 31

Hydrogen bonding between molecules in ice results in an expanded structure

Question 32

What are ionic compounds and polar molecules soluble in

Answer 32

Polar solvents e.g. water (like dissolves like)

Question 33

What are ionic compounds and polar molecules insoluble in

Answer 33

Non-polar solvents

Question 34

What are non-polar molecular substances soluble in

Answer 34

Non-polar solvents (like dissolves like)

Question 35

What are non-polar molecular substances insoluble in

Answer 35

Polar solvents

Question 36

What are the key features to consider when predicting the solubility of a compound

Answer 36

- presence of hydrogen bonding in molecules (O-H or N-H) | - spatial arrangement of polar covalent bonds