Topic 1 - Atomic structure and the periodic table

Question 1

What is usually the radius of an atom?

Answer 1

0.1 nanometres (1 x 10^-10)

Question 2

Does the nucleus of an atom have:
- positive charge
- negative charge
- no charge

Answer 2

positive charge

Question 3

What determines the size of an atom?

Answer 3

the volume of the electrons orbit

Question 4

What does the atomic number of an atom tell you?

Answer 4

how many protons are in the atom

Question 5

What does the mass number of an atom tell you?

Answer 5

total number of protons and neutrons in the atom

Question 6

What is an isotope?

Answer 6

atoms of the same element with the same number of protons but different numbers of neutrons (same atomic number, different mass number)

Question 7

What is filtration used to seperate?

Answer 7

insoluble solids from a liquid
purification ( seperate out solid impurities)

Question 8

Name two ways you can seperate soluble solids from a solution

Answer 8

• evaporation
• crystallisation

Question 9

Describe the method of evaporation to seperate soluble solids from a solution (3 steps)

Answer 9

1. pour the solution into an evaporating dish
2. slowly heat the solution. the solvent will evaporate and the solution wil become more concentrated. Eventually crystals will form
3. keep heating until you are left with dry crystals

Question 10

Why might evaporation not always work to seperate soluble solids from solutions? what other method could you use?

Answer 10

it only works if the salt doesnt decompose when heated up
crystalisation

Question 11

Describe the method of crystallisation to separate soluble olids from solutions (4 steps)

Answer 11

1. Pour the solution into an evaporating dish and gently heat the solution. ( some of the solution will evaporate and the solution will get more concentrated)
2. once some of the solvent has evaporated or when crystals start to form (point of crystallisation), remove the dish from the heat and leave the solution to cool
3. the salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
4. filter the crystals out of the solution and leave them in a warm place to dry.

Question 12

DEscribe how you can use filtration, evaporatio and crystallisation to seperate rock salt and why these methods would be used

Answer 12

1. rock salt is a mixture of rock and sand.
   salt dissolves in water and sand doesnt

1) grind the mixture to make sure the salt crystals are small, so they will disolve easily
2) put the mixture in water and stir. (the salt will dissolve but the sand wont)
3. filter the mixture to collect the sand. (the sand wont fit throughtthe filter paper so they collect on the paper instead. the salt pases through the paper )
4) Evaporate the water from the salt so that it forms dry crystals (or use crystallisation if you want bigger crystals)

Question 13

What is simple distillation used for?

Answer 13

seperating a liquid from a solution

Question 14

DEscribe the method of simple distillation (3 steps)

Answer 14

1. the solution is heated (the part of the solution that has the lowest boiling point evaporates first)
2. the vapour is then cooled and condensed in the condenser, it i then collected.
3. the rest of the solution is left behind in the flask

Question 15

Give an example of a solution u can seperate usinf simple distillation

Answer 15

seawater
pure water is evaporated, condensed and collected leaving behind salt in the flask

Question 16

What is the problem with simple distillation/ why does it not always work?

Answer 16

it can only be used to seperate substances with very different boiling points( if the temp goes higher than the temp of the substance with a higher boiling point, all the solution will be evaporated, condensed and collected together and the solution wil be mixed again)

Question 17

What is the name of the group 0 elements?

Answer 17

noble gases

Question 18

Why are noble gases unreactive?

Answer 18

they all have a full outer shell of electrons meaning they dont need to give up or gain electrons to become stable

Question 19

Name 4 features of noble gases

Answer 19

1. they are unreactive (full outer shell, stable)
2. they exist as monatomic gases (single atoms not bonded to eachother)
3. colourless gases at room temperature
4. non- flammable

Question 20

The boiling point and Ar (relative atomic mass) of noble gases increases as you move ________ the group

Answer 20

down

Question 21

Why does the boiling point increase as you go down group 0?

Answer 21

as you go down the group, the number of electrons in each atom increases leading to greater intermolecular forces between them which need more energy to overcome.