Chemistry Atomic structure, Covalent bonding and Metallic bonding half term test

Question 1

What’s the order of the development of the atomic models?

Answer 1

• Greeks said that atoms are tiny spheres that cannot be divided
• Plum pudding model, a ball of positive charge with electrons embedded in it
• Alpha particle scattering experiment, showed that the mass of an atom is concentrated at the centre and the nucleus is charged
• Positively charged nucleus orbited by electrons like planets around the sun
• Niels Bohr adopted the nuclear model by suggesting that the electrons orbit at specific distances

Question 2

Definition of atom

Answer 2

Smallest part of an element that can exist

Question 3

Definition of element

Answer 3

Contains only one type of atom

Question 4

Definition of compound

Answer 4

consists of two or more elements or compounds that are chemically combined

Question 5

How to calculate relative atomic mass

Answer 5

Total mass of atoms/ total number of atoms

Question 6

What are isotopes?

Answer 6

atoms of the same element but with different numbers of neutrons therefore different masses.

Question 7

Who discovered the neutron?

Answer 7

James Chadwick

Question 8

What is covalent bonding?

Answer 8

When atoms share pairs of electrons. (strong bond)

Question 9

Advantages of displayed formula

Answer 9

• quick and easy to draw and identify
• shows how they are bonded to each other

Question 10

Advantages of ball and stick models

Answer 10

• shows the shape of the molecule
• 3D
• shows which atoms are bonded to which

Question 11

Advantages of dot and cross diagrams

Answer 11

• shows which atoms are bonded to each other
• shows electrons

Question 12

Disadvantages of displayed formula

Answer 12

• 2D
• cannot see electrons

Question 13

Disadvantages of ball and stick models

Answer 13

• does not show electrons
• hard to draw when there are many atoms

Question 14

Disadvantages of dot and cross diagrams

Answer 14

• does not show electrons orbiting
• hard to draw if there are many atoms
• 2D

Question 15

Size of atom

Answer 15

1 nanometer (1x10^-10m)

Question 16

Size of nucleus

Answer 16

About 1x10^-14m

Question 17

Difference between simple and giant covalent structures

Answer 17

simple covalent structures have a fixed number of atoms (eg. ammonia) and giant covalent structures have large and variable amounts of atoms

Question 18

Properties of giant covalent structures

Answer 18

• high boiling and melting points (strong intermolecular forces)
• strong (covalent bonds)
• cannot conduct electricity (except for graphite and graphene)
• has a lattice structure
• not soluble in water

Question 19

Properties of simple covalent molecules

Answer 19

• low boiling and melting points
• weak intermolecular forces
• do not conduct electricity as they do not have an overall electric charge

Question 20

What are polymers?

Answer 20

large molecules with many small repeating units called monomers that are joined with strong covalent bonds

Question 21

Definition of mixture

Answer 21

A mixture consists of two or more elements or compounds that are not chemically combined

Question 22

What is graphene?

Answer 22

A single layer of graphite

Question 23

Properties of graphene

Answer 23

• very high melting point
• very strong
• conducts electricity well due to having delocalised electrons
• often used in electronics and composites

Question 24

What are fullerenes?

Answer 24

• Molecules of carbon atoms with hollow shapes
• based on hexagonal rings of carbon atoms but may also contain rings of five or seven carbon atoms

Question 25

What was the first fullerene that was discovered?

Answer 25

Buckminsterfullerene (C60)

Question 26

Properties of fullerenes

Answer 26

- low melting and boiling point (weak intermolecular forces - cage like structure (can transport substances inside it eg. medicine) - good catalyst (large surface area compared to volume) - has a delocalised electron that can carry the charge - lightweight

Question 27

Are the intermolecular forces of polymers strong

Answer 27

yes, so they remain as solids at room temperature

Question 28

How is ethene converted to polyethene?

Answer 28

the double covalent bond between the carbon atoms are broken and is joined to a neighboring molecule

Question 29

Draw the shorthand way of representing a polymer

Answer 29

(see goodnotes)

Question 30

Compare diamond to graphite

Answer 30

(see goodnotes)

Question 31

Where do we find metals on the periodic table?

Answer 31

on the left

Question 32

What is metallic bonding?

Answer 32

- A strong electrostatic force of attraction between positive and delocalised electrons as the delocalised electrons are free to move through (not throughout) the whole structure, leaving positive ions.

Question 33

Advantages of the 2D diagram of metallic bonding

Answer 33

- can see the "sea" of electrons - can see every atom easily (none are blocked or covered)

Question 34

Advantages of the 3D diagram of metallic bonding

Answer 34

- shows layer arrangement of the atoms and the giant lattice structure

Question 35

Disadvantages of the 2D diagram of metallic bonding

Answer 35

- cannot see the layer arrangement of the atoms/ the giant lattice structure - doesn't show each indivual electron

Question 36

Disadvantages of the 3D diagram of metallic bonding

Answer 36

- doesn't show electrons at all - can only see outermost atoms

Question 37

Properties of metals

Answer 37

- **high melting and boiling point:** strong electrostatic forces of attraction so it takes a lot of thermal energy to break the bond - **malleable**: metals consist of layers of ions that are the same size that can slide over each other when the metal is bent, hammered, or pressed - **electrical conductor:** delocalised electrons can carry electrical charge through the metal and move through the structure

Question 38

Why are alloys stronger and harder than pure metals

Answer 38

- the layers are distorted so the particles cannot slide over each other as well

Question 39

Why do alloys not conduct as well as pure metals

Answer 39

- distorted layers cause the delocalised electrons to not be able to pass through the structure as easily.

Question 40

Describe ionic bonding

Answer 40

the metal atom loses its outermost electrons and transfers them to the non metal atom to complete the non metal atom's outer shell. This makes the metal atom a positive ion and the non metal atom a negative ion as there aren't enough electrons to balance the charge of the protons and vice versa. there is a strong electrostatic force of attraction between the oppositely charged ions

Question 41

Properties of ionic compounds

Answer 41

- **high melting and boiling point** : the lattice structure and the strong electrostatic forces between the ions require a lot of thermal energy to break - **Crystalline** : this reflects the regular arrangement of teh ions - **brittle** : small distortions in the crystal bring ions with the same charge together and similar charges repel each other, breaking the crystal apart - **soluble in water** : the slightly negative oxygen in the water attracts the positive ions while the slightly negative hydrogen in the water attracts negative ions, pulling the crystal apart - **do not conduct when solid** : the ions cannot move when the ionic compound is solid there cannot carry any charge and cannot conduct electricity - **conduct when molten/ in solution** : the ions are free to move when molten or dissolved and will carry the charge and conduct electricity

Question 42

Draw a ionic bonding diagram for sodium chloride

Answer 42

see goodnotes