Atomic Structure and the Periodic Table

Question 1

What is the radius of an atom?

Answer 1

0.1 nanometres (1 x 10^-10)

Question 2

Describe the nucleus?

Answer 2

1) It’s in the middle of the atom
2) It contains protons and neutrons
3) It has a positive charge because of the protons
4) The nucleus has a radius of 1x10^-14 metres
5) Almost the whole mass of the atom is concentrated in the nucleus

Question 3

Describe the electrons?

Answer 3

1) Move around the nucleus in electron shells
2) They are negatively charged and tiny but they cover a lot of space
3) The volume of their orbits determines the size of the atom
4) Electrons have virtually no mass

Question 4

What is the mass of a proton, neutron and electron?

Answer 4

The mass of a proton = 1, neutron = 1 and electron = negligible

Question 5

What is the charge of a proton, neutron and electron?

Answer 5

The charge of a proton = +1, neutron = 0 and electron = -1

Question 6

Why do atoms have no charge overall?

Answer 6

The number of protons = the number of electrons
This means the charges cancel out

Question 7

Why do ions have a charge?

Answer 7

The number of protons ≠ the number of electrons

Question 8

What does the nuclear symbol of an atom show?

Answer 8

Its atomic number and mass number

Question 9

What does the atomic number show?

Answer 9

How many protons there are

Question 10

What does the mass number show?

Answer 10

The total of number of protons and neutrons in the atom

Question 11

What is an element?

Answer 11

It is a substance made up of atoms that all have the same number of protons in their nucleus.

Question 12

What are isotopes?

Answer 12

They are different forms of the same element - they have the same number of protons but a different number of neutrons.

Question 13

What is the relative atomic mass?

Answer 13

An average mass taking into account the different masses and abundances of all the isotopes that make up the element.

Question 14

What is the equation for the relative atomic mass?

Answer 14

relative atomic mass = (sum of (isotope abundance x isotope mass number)) ÷ sum of abundance of all the isotopes

Question 15

What are compounds?

Answer 15

A pure substance made from more than one type of element chemically bonded together.

Question 16

How can compounds be represented?

Answer 16

By formulas.

Question 17

What is a mixture?

Answer 17

A mixture contains two or more substances not chemically combined together.

Question 18

What are the ways of separating substances in a mixture?

Answer 18

1) Chromatography
2) Filtration
3) Crystallisation
4) Distillation
5) Magnetism
6) Manual Separation
7) Evaporation

Question 19

Describe a method for chromatography?

Answer 19

1) Draw a line near the bottom of a sheet of filter paper (use a pencil to do this as pencil marks are insoluble and won’t dissolve in the solvent)
2) Add a spot of the ink to the line and place the sheet in a beaker of solvent (e.g. water)
3) The solvent used depends on what’s being tested. Some compounds dissolve well in water, but sometimes other solvents, like ethanol, are needed
4) Make sure the ink isn’t touching the solvent - you don’t want it to dissolve into it
5) Place a lid on top of the container to stop the solvent evaporating
6) The solvent seeps up the 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 dye will form a spot in a different place - 1 spot per dye in the ink
8) If any of the dyes in the ink are insoluble in the solvent you’ve used, they’ll stay on the baseline
9) When the solvent has nearly reached the top of the paper, take the paper out of the beaker and leave it to dry
10) The end result is a pattern of spots called a chromatogram

Question 20

What does filtration do?

Answer 20

It separates insoluble solids from liquids. Or can be used for purification if there are solid impurities in a liquid reaction mixture.

Question 21

What does soluble and insoluble mean?

Answer 21

Insoluble: the solid cannot be dissolved in the liquid
Soluble: the solid can be dissolved in the liquid

Question 22

What are two ways to separate soluble solids from solutions?

Answer 22

1) Evaporation
2) Crystallisation

Question 23

How does evaporation separate soluble solids from solutions as a method?

Answer 23

1) Pour the solution into an evaporating dish.
2) Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually, crystals will start to form.
3) Keep heating the evaporating dish until all you have left are dry crystals.

Question 24

What are the advantages and disadvantages of using the evaporation technique to separate soluble solids from solutions?

Answer 24

Advantages: Really quick
Disadvantages: Only can use this method if the salt doesn’t decompose (break down)

Question 25

How does crystallisation separate soluble solids from solutions as a method?

Answer 25

1) Pour the solution into an evaporating dish and gently heat the solution. Some of the solvent will evaporate and the solution will get more concentrated.
2) Once some of the solvent has evaporated, or when you see crystals start to form (the 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. You could also use a drying oven or a desiccator.

Question 26

What is rock salt?

Answer 26

A mixture of salt and sand.

Question 27

What techniques can separate rock salt?

Answer 27

1) Filtration
2) Crystallisation

Question 28

Why is rock salt easy to separate?

Answer 28

Salt = soluble compound
Sand = insoluble compound

Question 29

Describe a method to separate rock salt?

Answer 29

1) Grind the mixture to make sure the salt crystals are small so will dissolve easily
2) Put the mixture in water and stir. The salt will dissolve, but the sand won’t
3) Filter the mixture. The grains if sand won’t fit through the tiny holes in the filter paper, so they collect on the paper instead. The salt passes through the filter paper as its part of the solution.
4) Evaporate the water from the salt so that it forms dry crystals.

Question 30

What is simple distillation used for?

Answer 30

To separate the liquid from a solution.

Question 31

Describe the method of simple distillation to separate out solutions?

Answer 31

1) Heat the solution. The part of the solution that has the lowest boiling point evaporates first.
2) The vapor then cools, condenses and is collected.
3) The rest of the solution is left behind in the flask.

Question 32

Label a diagram for simple distillation and fractional distillation?

Answer 32

Check page.18

Question 33

What does distillation often separate?

Answer 33

Seawater to get pure distilled water.

Question 34

What is the problem with distillation?

Answer 34

You can only separate substances with very different boiling points.

Question 35

What is fractional distillation used for?

Answer 35

To separate a mixture of liquids.

Question 36

How does one perform the method of fractional distillation?

Answer 36

1) Put you mixture in a flask and stick a fractionating column on top
2) Heat your mixture
3) The different liquids will have different boiling points so they will evaporate at different temperatures
4) The liquid with the lowest boiling point evaporates first - once the thermometer matches the boiling point of this liquid, it will reach the top of the column
5) The column is cooler at the top than at the bottom so they will only get part of the way up before condensing and running back down towards the flask
6) Once the first liquid has been collected, raise the temperature until the next one reaches the top

Question 37

Describe the history of the atom?

Answer 37

1) In the 19th century, John Dalton said atoms were solid spheres and that different spheres made up the different elements
2) In 1897, J J Thompson discovered neutrons and said atoms weren’t solid spheres but positively charged balls with negatively charged electrons embedded in them - this was known as the plum pudding model
3) In 1909, Ernest Rutherford and his student Ernest Marsden conducted the famous alpha particle scattering experiment - he created the nuclear model of the atom which showed most of the mass was concentrated in the centre of the atom in the positively charged nucleus and a cloud of negative electrons surrounds this nucleus so most of the atom was empty space
4) A cloud of negative electrons would mean it would be attracted to nucleus which would cause the atom to collapse - so in 1913 Niels Bohr proposed electrons orbit the nucleus in fixed shells with a fixed distance away from the nucleus
5) Further experiments by Rutherford showed that the nucleus could be divided into smaller particles which have the same charge as a hydrogen nucleus - these particles were named protons
6) 20 years after the acceptance of nuclei, James Chadwick carried out an experiment which provided evidence for neutral particles in the nucleus which are now called neutrons

Question 38

What was the alpha scattering experiment?

Answer 38

• He did this by firing a beam of alpha particles at a thin gold foil
• If the atom was like the plum pudding model it would have passed straight through or only be slightly deflected
• However, the results were that most passed straight through the sheet, some were deflected more than expected, a few were deflected back the way they came

Question 39

Where are electrons located?

Answer 39

In the shells

Question 40

What are the shells in an atom also known as?

Answer 40

The energy levels.

Question 41

Where are the lowest energy levels in an atom?

Answer 41

These are the closest shells to the nucleus.

Question 42

How many electrons are allowed in the:
1st shell
2nd shell
3rd shell

Answer 42

1st = 2 electrons
2nd = 8 electrons
3rd = 8 electrons

Question 43

Do you know how to drawn electron configurations as diagrams?

Answer 43

Check pg. 20

Question 44

What is the electronic configuration for a sodium atom?

Answer 44

2.8.1

Question 45

When is an atom stable?

Answer 45

When they have a full outer shell. If is is not full this makes the atom want to react to fill it.

Question 46

Until recently, what were the two ways to categorise elements?

Answer 46

1) Their physical and chemical properties
2) Their atomic weight

Question 47

Before recently, how was the periodic table arranged?

Answer 47

The tables were not complete and some elements were in the wrong group as it was in order of their atomic weight as well as their properties not being taken into account.

Question 48

What did Dmitri Mendeleev do?

Answer 48

1) In 1869, he took 50 known elements and arranged them into his Table of Elements with various gaps
2) He put the elements mainly in order of atomic weight but did switch that order if the properties meant it should be changed - an example of this is with Tellurium and Iodine, iodine has a smaller atomic weight but is placed after tellurium as it has similar properties to the elements in that group
3) Gaps were left in the table to ensure elements with similar properties stayed in the same groups, some of these gaps indicated the existence of undiscovered elements - this allowed Mendeleev to predict what their properties might be (when they were found and fitted the pattern it helped confirm Mendeleev’s ideas) - an example is when Mendeleev made predictions about the chemical and physical properties of an element that he called ekasilicon which we know today as germanium

Question 49

How is the modern periodic table laid out?

Answer 49

In order of increasing atomic number. This means there are repeating patterns in the properties of the elements.

Question 50

Do you know the different parts of the periodic table and what they mean?

Answer 50

Check pg.22

Question 51

Elements with similar properties form what on the periodic table?

Answer 51

Columns. These are called groups.

Question 52

What does a group number represent?

Answer 52

The amount of electrons those elements have in their outer shell.

Question 53

What are the rows called in a periodic table?

Answer 53

Periods which represents the number of electron shells in an element.

Question 54

What metal ions form?

Answer 54

Positive ions when they react.

Question 55

What non-metal ions form?

Answer 55

Negative ions when they react.

Question 56

What happens to the outer shell if it is far away from the nucleus?

Answer 56

The electrons have a weaker attraction.

Question 57

What do all metals have?

Answer 57

Metallic bonding which causes them to have similar physical properties.

Question 58

What are some properties of metals?

Answer 58

1) They’re strong
2) They’re malleable
3) They can conduct heat and electricity
4) They have high melting and boiling points

Question 59

What are some properties of non-metals?

Answer 59

1) Dull looking
2) Brittle
3) Not always a solid at room temperature
4) Don’t normally conduct electricity
5) They often have a lower density

Question 60

What are the properties of transition metals?

Answer 60

1) Good conductors of heat and electricity
2) They are very dense
3) Strong
4) Shiny
5) They can have more than one ion - e.g. copper and cobalt
6) They are often coloured and so compounds that contain them are colourful - e.g. potassium chromate and potassium manganate
7) Often make good catalysts - e.g. nickel for hydrogenation of alkenes and iron for the Haber process for making ammonia

Question 61

What are the group 1 metals called?

Answer 61

The alkali metals.

Question 62

Why are the group 1 metals reactive?

Answer 62

They have only one electron in their outer shell.

Question 63

What are the properties for the alkali metals?

Answer 63

1) They are soft
2) They have a low density
3) They are very reactive

Question 64

What are the trends for the group 1 metals?

Answer 64

• Increasing reactivity as you go down the column - outer electron is easily lost as the attraction between the nucleus and the electron decreases, because the electron is further away from the nucleus
• Melting and boiling points decrease as you go down the column
• The relative atomic mass increases as you go down the column