2.4 Structure and Bonding

Question 1

Electron pair geometry

Answer 1

How regions of electron density arrange themselves around a central atom

Question 2

Trigonal pyramid

Answer 2

A molecular geometry with four regions of electron density and one lone pair

Question 3

Tetrahedron

Answer 3

A molecular geometry with four regions of electron density and no lone pairs

Question 4

V-shaped (bond angle of 109.5°)

Answer 4

A molecular geometry with four regions of electron density and two lone pairs

Question 5

V-shaped (bond angle of 120°)

Answer 5

A molecular geometry with three regions of electron density and one lone pair

Question 6

Trigonal planar

Answer 6

A molecular geometry with three regions of electron density and no lone pairs

Question 7

What is VSEPR theory?

Answer 7

Valence Shell Electron Pair Repulsion theory states that regions of electron density will arrange themselves as far apart from each other as possible, so as to minimise the repulsion felt between them

Question 8

Electronegativity

Answer 8

A measure of an atom’s TENDENCY to attract bonding electrons to itself

Question 9

Why do the elements in group 18 have no electronegativity?

Answer 9

The elements in group 18 all have full valence shells. They do not need to bond to gain or lose electrons, so they do not attract bonding electrons to themselves

Question 10

Dipole

Answer 10

The separation of positive and negative charges (a polar bond creates a dipole)

Question 11

Covalent bond

Answer 11

The bond between two atoms that forms when a pair of electrons is shared between them

Question 12

Brittle

Answer 12

A property of a substance that describes how a substance will snap/ shatter when a force is applied

Question 13

Delocalised electrons

Answer 13

Electrons that are not assigned to one specific atom, but are free to move around the structure

Question 14

Ductility

Answer 14

The ability of a substance to be stretched into wires when a force is applied

Question 15

Endothermic reactions

Answer 15

Chemical reactions involving a transfer/ ABSORPTION of energy from the surroundings into the system

Question 16

Exothermic reactions

Answer 16

Chemical reactions involving a transfer/ RELEASE of energy from the system into the surroundings

Question 17

Intermolecular forces

Answer 17

The attractive forces that occur BETWEEN molecules, holding them together

Question 18

Intramolecular forces

Answer 18

The attractive forces that occur WITHIN individual molecules, holding the atoms that make up that molecule together

Question 19

Ionic bond

Answer 19

The electrostatic attraction that occurs between positively charged cations and negatively charged anions

Question 20

Malleability

Answer 20

A substance’s ability to be bent into different shapes when a force is applied. Can usually be hammered/ rolled into thin sheets.

Question 21

Metallic bond

Answer 21

The electrostatic attraction between positively charged metal nuclei and the negatively charged delocalised electrons

Question 22

Soluble

Answer 22

Whether or not a substance can be dissolved in a liquid (the solvent)

Question 23

System

Answer 23

All the energy and matter (particles/ molecules) involved in a chemical reaction

Question 24

What are the elements in group 1 called?

Answer 24

Alkali metals

Question 25

What are the elements in group 2 called?

Answer 25

Alkali earth metals

Question 26

Radioisotope

Answer 26

An isotope that is unstable and undergoes radioactive decay

Question 27

What are the elements in groups 3-12 called?

Answer 27

Transition metals

Question 28

Alloy

Answer 28

A metallic bond that occurs between different metals or with non-metals

Question 29

What direction are metal bonds?

Answer 29

Metallic bonds are non-directional, as electrons are equally attracted to all the cations in the structure, and can move between them randomly

Question 30

Electrostatic attraction

Answer 30

The attractive forces between oppositely electrically charged objects

Question 31

Why are metals insoluble in ANY type of solvent?

Answer 31

The metallic bond between the delocalised electrons and nuclei is too strong to be overcome by the attractive forces between the solvent and the particles within the metal

Question 32

Why do metals have high electrical conductivity?

Answer 32

Electrical conductivity requires a substance to have free-moving, charged particles in order for it to carry an electrical current. Metals have negatively charged, delocalised electrons that are free to move throughout the metal lattice. When a current is applied to a metal. the delocalised electrons will be attracted to the positive electrode and can move through the metal lattice towards it. Therefore this allows current to flow

Question 33

Why are metals malleable/ ductile?

Answer 33

The particles in metals can move past each other and remain strongly bonded. When metal nuclei are forced into a new position, they will still experience strong electrostatic bonding with the delocalised electrons around them due to non-directional bonding. So the metal nuclei can slide past each other and settle into a new position once there is no longer a force

Question 34

Why do most metals have high melting points?

Answer 34

The strong forces of attraction between delocalised electrons and their positive nuclei are difficult to overcome and require a lot of heat energy to do so

Question 35

Why are metals dense?

Answer 35

The cations are packed tightly together in a rigid lattice

Question 36

Molecular substances

Answer 36

Substances made up of multiple molecules packed together

Question 37

Why CAN'T a polar solute dissolve in a non-polar solvent?

Answer 37

The molecules in the solute are unable to interact strongly with the molecules in the solvent. The forces of attraction between the different molecules in much stronger than any potential forces of attraction between the solvent and the solute. They will therefore remain in separate layers.

Question 38

Why CAN a polar solute dissolve in a polar solvent?

Answer 38

The solute-solute and solvent-solvent forces are of similar strength. This means that the two can interact strongly with each other. The intermolecular forces between the solute molecules will be broken, and the individual molecules will form new intermolecular forces with the solvent molecules.

Question 39

Polyatomic ions

Answer 39

Charged particles made up of groups of atoms that act as a single unit in an ionic compound