Topic 1 - Atomic Structure And Periodic Table

Question 1

Masses of particles

Answer 1

Protons: 1
Neutron: 1
Electron: very small

Question 2

Charge of particles

Answer 2

Proton: +1

Neutron: 0

Electron: -1

Question 3

Why atoms are neutral

Answer 3

Have no charge overall as number of protons is the same as electrons (unlike ions)

Question 4

Isotope definition

Answer 4

Different forms of the same element which have the same number of protons but a different number of neutron

Giving them the same atomic number but different mass

Question 5

Formula of relative atomic mass of an element

Answer 5

RAM= sum of (isotope abundance x isotope mass number/ sum of abundances of all the isotopes)

Question 6

What is a compound

Answer 6

Substances formed from two or more elements

Held together by chemical bonds

Making bonds involved atoms taking or giving electrons - only electrons involved

It’s usually difficult to separate the original elements of a compound out again - chemical reaction is needed

Question 7

Why are mixtures easily separated

Answer 7

There is no chemical bond between the different parts of the mixture

Question 8

Method of chromatography

Answer 8

1) draw line near bottom of filter paper(in pencil as it is insoluble)
2) add a spot of ink to the line and place sheet in beaker of solvent
3) solvent used depends on what’s being tested.
4) make sure ink isn’t touching solvent as it may dissolve into it
5) place kid on top of container to stop solvent evaporating
6) solvent seeps up paper carrying the ink with it
7) each different dye in the ink will move up the paper at a different rate so the dyes will separate out. Each due will form a spot in a different place
8) if any of the dyes are insoluble they will stay on the baseline
9) when the solvent has nearly reached the top of the paper take it out the beaker and leave to dry
10) end result is a chromatogram

Question 9

Two ways to separate soluble solids from solutions

Answer 9

Evaporation

Crystallisation

Question 10

Evaporation method

Answer 10

1) pour solution into evaporating dish
2) slowly heat the solution. Solvent will evaporate and solution will get more concentrated. Eventually, crystals will start to form
3) keep hearing the evaporating dish until all you have left is dry crystals

Question 11

Crystallisation

Answer 11

1) pour solution into evaporating dish and entry heat the solution. Some solvent will evaporate and the solution will get more concentrated
2) once some solvent has evaporated or when crystals start to form, remove the dish from heat and leave 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 in a warm place to dry

Question 12

Simple distillation method : used to separate solutions

Answer 12

1) solution is heated . Part of solution with lowest boiling point evaporates first
2) vapour is then cooled, condensed and is collected
3) Rest of solution is left behind in flask

Question 13

Problems with simple distillation

Answer 13

Can only be used to separate things with very different boiling points - if temp goes higher than boiling point of the substance with the higher boiling point they will mix again

Question 14

Fractional distillation method : used to separate mixture of liquids

Answer 14

1) put mixture in flask and put fractionating column on top, then heat
2) different liquids will all have different boiling points so will evaporate at diff. temperatures
3) liquid with lowest boiling point evaporated first. When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column
4) liquids with higher boiling points might also start to evaporate , but the column is cooler towards the top. So they will only get part of the way up before condensing and running back down towards the flask
5) when the first liquid has been collected, raise the temperature until the next one reaches the top

Question 15

Development of the atomic structure

Answer 15

1) start of 19th century John Dalton described the atoms as solid spheres and that different spheres made up different elements
2) 1897- JJ Thompson concluded atoms weren’t solid spheres. His measurements of charge and mass showed the atom must contain even smaller, negatively charged particles called electrons
3) this new theory was called the ‘plum pudding model’ and it showed the atom was a ball of positivel charge with electrons stuck in

Question 16

How Rutherford showed the plum pudding model was wrong

Answer 16

In 1909 Rutherford conducted the famous ‘alpha particle scattering experiments’ where they fired positively charged alpha particles at an extremely thin sheet of gold

From the plum pudding model they expected the particles to pass straight through or be slightly deflected at most as the positive charge of each atom was thought to be very spread out within the atom. Although most particles did pass straight through , some were deflected more than expected.

Rutherford came up with the hypothesis that there is a tiny positively charged nucleus at the centre where most mass is concentrates and a cloud of negative electrons surrounded the nucleus so most of the atom is empty space

Question 17

Why Dmitri left gaps in the early periodic table

Answer 17

To make sure elements with similar properties stayed in the same groups. Some of the gaps indicated the existence of undiscovered elements and allowed Mendeleev to predict what their properties might be

Question 18

In the modern periodic table what forms columns

Answer 18

Elements with similar properties

These vertical columns are called groups

Question 19

What does the group number tell in the modern periodic table

Answer 19

How many electrons are in the outer shell

This means all elements in the same group will react similarly

Question 20

Reactivity in group 1

Answer 20

Elements react more vigorously as you go down the group

Question 21

Reactivity in group 7

Answer 21

Reactivity decreases as you go down the group

Question 22

What are the rows in the modern periodic table

Answer 22

Periods

Each new period represented another full shell of electrons

Question 23

Metal physical properties

Answer 23

• strong but malleable
• great at conducting heat and electricity
• have high bp and mp

Question 24

Non metal physical properties

Answer 24

• more brittle as they aren’t always solids
• don’t generally conduct electricity
• lower density

Question 25

Properties of transition metals

Answer 25

• more than one ion
• coloured and so compounds that contain them are colourful
• often make good catalysts

Question 26

Group 1 elements

Answer 26

Alkali metals:

• soft and have low density
• all have one electron in outer shell (making them very reactive and gives them similar properties)

Question 27

Trends of alkali metals as you go down group 1

Answer 27

1) increasing reactivity - outer electron is more easily lost as the attraction between the nucleus and electron decreases because the electron is further away from nucleus as there are more energy levels as you go down
2) lower melting and boiling points
3) higher relative atomic mass

Question 28

Reactions of alkali metals with non metals

Answer 28

Water:
React vigorously to produce hydrogen gas and metal hydroxides

Chlorine:
React vigorously when heated in chlorine gas to form white metal chloride salts

Oxygen:
React to form a metal oxide

Question 29

Trends of group 7 as you go down the group

Answer 29

• become less reactive - its harder to gain an extra electron because the outer shell is further away from the nucleus
• have higher bp and mp
• have higher relative atomic mass

Question 30

Group 0 elements

Answer 30

Called the noble gases

All have 8 electrons in outer shell

As their outer shell is energetically stable they don’t need to give or gain electrons to become more stable - this means they don’t react with much at all

They exist as monatomic gases - single atoms not bonded to each other

All are colourless gases at room temp

They’re non flammable

Question 31

Patterns in the properties of noble gases

Answer 31

1) boiling points increase as you move down the group along with increasing RAM
2) increase in bp is due to increase in number of electrons in each atom leading to greater intermolecular forces between them which need to be overcome