Topic 1 - Key Concepts

Question 1

define aqueous

Answer 1

dissolved in water

Question 2

symbol for ammonia

Answer 2

NH3

Question 3

symbol for oxygen

Answer 3

O2

Question 4

symbol for chlorine

Answer 4

Cl2

Question 5

symbol for ammonium ions

Answer 5

NH4 +

Question 6

symbol for nitrate ions

Answer 6

NO3-

Question 7

symbol for carbonate ions

Answer 7

CO3 2-

Question 8

symbol for sulphate ions

Answer 8

SO4 2-

Question 9

how do you do ionic equations from a full chemical equation

Answer 9

break up aqueous products and reactants into ions
cross out what is the same on both sides
re write with remaining ions

Question 10

define hazard and risk

Answer 10

a hazard is anything that has the potential to cause harm or damage
the risk associated with that hazard is the probability of someone or something being harmed if they are exposed to that hazard

Question 11

discuss John Daltons model of the atom

Answer 11

at the beginning of the 1800’s (19th century) Dalton described atoms as solid spheres for the different elements

Question 12

discuss JJ Thompsons model of the atom

Answer 12

In 1897 he concluded from his experiments that atoms were not solid spheres

• his measurements of charge and mass showed that an atom must contain even smaller, negatively charged particles called electrons
• the ‘solid sphere’ idea of atomic structure had to be changed
• new theory was the plum pudding model which was a positively charged pudding with electrons throughout

Question 13

what was Rutherford’s model of the atom

Answer 13

there is a tiny positively charged nucleus at the centre surrounded by a cloud of negative electrons and most of the atom is empty space

Question 14

what was the refined Bohr model of the atom

Answer 14

Scientists realised that electrons in a cloud around the nucleus of an atom would cause it to collapse because they would be attracted to the positive nucleus

Niels Bohr proposed a new model of the atom where all the electrons were contained in shells

Bohr suggested that electrons can only exist in fixed orbits or shells and not anywhere in between.
each shell has a fixed energy

Question 15

define isotope

Answer 15

different forms of the same element which have the same number of protons and electrons but a different number of neutrons
the same atomic number but different mass numbers

Question 16

define relative atomic mass

Answer 16

the relative atomic mass of an element is the average mass of one atom of the element compared to 1/12 of the mass of one atom of carbon-12

Question 17

how does Dimitri Mendeleev’s version of the periodic table compare to ours

Answer 17

Mendeleev:

• based on their properties and properties of their compounds
• order of atomic mass
• similar chemical properties in columns

Ours:

• order of atomic number
• similar chemical properties
• groups with outer shell electrons
• periods

Question 18

what is the overall charge of any ionic compound

Answer 18

0 because the charges balance each other out

Question 19

what is ionic bonding

Answer 19

when a metal and non metal react together
the metal atom loses electrons to form a positive ion (cation) and the non-metal gains electrons to from a negative ion (anion)
these oppositely charged ions are attracted together by electrostatic forces of attraction

Question 20

how do you show an ionic bond

Answer 20

dot and cross diagram

Question 21

describe the structure of ionic compounds

Answer 21

• giant ionic lattice structures
• the ions form a closely packed regular lattice of oppositely charged ions
• there are very strong electrostatic forces of attraction between oppositely charged ions in all directions

Question 22

describe the properties of ionic compounds

Answer 22

• high mp and bp due to strong attractions between the ions so it takes a large amount of energy to overcome this attraction
• solid ionic compounds don’t conduct electricity because the ions are fixed in place and can’t move
• molten ionic compounds can conduct because the electrons are free to move and carry a current
• many dissolve easily in water, the ions separate and are all free to move in the solution so they’ll carry an electric current

Question 23

describe the properties of simple molecular substances

Answer 23

• substances containing covalent bonds usually have simple molecular substances
• the atoms within the molecules are held together by very strong covalent bonds but the forces of attraction between these molecules are very weak
• to melt or boil a simple molecular substance you only need to break these feeble intermolecular forces and not the covalent bonds so mp an bp’s are very low because the molecules are easy to part from each other
  most molecular substances are gases or liquids at room temperature
• as molecules get bigger the strength of intermolecular forces increases so more energy is needed to break them and the melting and boiling points increase
• molecular compounds don’t conduct electricity because they don’t contain any free electrons or ions

Question 24

describe the properties of giant covalent structures

Answer 24

• high mp and bp as all the atoms are bonded to each other by strong covalent bonds and a lot of energy is needed to break these bonds
• don’t conduct electricity (apart from graphite and graphene) because they don’t contain charged particles
• they aren’t soluble in water

Question 25

what are fullerenes

Answer 25

• molecules of carbon shaped like closed tubes or hollow balls
• mainly made up of carbon atoms arranged in hexagons but can also contain pentagons or heptagons
• can be used to ‘cage’ other molecules
• the fullerene structure forms around another atom or molecule which is then trapped inside
• this could be used to deliver a drug directly to cells in the body
• fullerenes have a huge surface area so they could help make great industrial catalysts
• individual catalyst molecules could be attached to the fullerenes, the bigger the surface area the better

Question 26

what are nanotubes

Answer 26

• are also fullerenes
• they are like tiny cylinders of graphene so they conduct electricity
• have a high tensile strength so don’t break when stretched and can be used to strengthen materials without adding much weight
• for example they can be used to strengthen sports equipment that needs to be strong but lightweight like tennis rackets

Question 27

what is buckminsterfullerene

Answer 27

• molecular formula C60
• forms a hollow sphere made up of 20 hexagons and 12 pentagons
• it is a stable molecule that forms soft brownish-black crystals

Question 28

describe the structure of a metal

Answer 28

a giant lattice structure of a regular arrangement of positive ions in a sea of delocalised electrons