Topic 1 Atomic structure

Question 1

What is the relative charge of a neutron? What is it’s relative mass?

Answer 1

Neutrons are neutral - relative charge is 0. The relative mass of a neutron is 1.

Question 2

What is an isotope?

Answer 2

different forms of the same element with have the same number of protons but a different number of neutrons.

Question 3

True or false? Most of the mass of an atom is located in the nucleus?

Answer 3

True. Electrons have virtually no mass.

Question 4

Why do atoms have no charge?

Answer 4

They have the same number of protons as electrons. Because the charges of the protons (+1) and the charges of the electrons (-1) are opposite and equally sized they cancel each other out.

Question 5

How do you calculate the number of neutrons the atom of an element has?

Answer 5

Number of neutrons = mass number - atomic number (usually the larger [at the top on AQA] minus the smaller)

Question 6

Why is the atomic mass of Chlorine not a whole number?

Answer 6

Chlorine has more than one isotope. Relative atomic mass is an average that takes into account the different masses and abundances of all the isotopes that make up an element.

Question 7

Freda is building a model of an atom. she wants to use her prize turnip as the nucleus. The turnip has a radius of 20cm. What will the radius of the whole atom be?

Answer 7

The radius of an atom is around 10,000 times the size of the radius of the nucleus. So 20cm x 10000 = 200,000cm cm to m = / by 100 200,000/100 = 2000m = 2km

Question 8

True or false? The properties of a compound are always similar to those of the elements that make it up.

Answer 8

False. Compounds often have totally different properties to the original elements.

Question 9

How many carbon atoms are there in a molecule of calcium carbonate, CaCO₃?

Answer 9

1

Question 10

What is a compound?

Answer 10

A compound is formed from two or more different elements in fixed proportions, held together by chemical bonds.

Question 11

Two atoms of Aluminium, Al, react with three atoms of oxygen, O, to form one molecule of Aluminium oxide. No other products are formed. What is the formula of Aluminium oxide?

Answer 11

No other productas are formed so both atoms of alumium and all three atoms of oxygen must end up in the aluminium oxide.

So the formula is Al₂O₃

Question 12

What type of process is needed to seperate a compound into it’s elements?

Answer 12

a chemical reaction

Question 13

What number needs to go in front of CO₂ to balance this equation?

C₆H₈O₇ + 3NaHCO₃ → CO₂ +3H₂O + Na₃C₆H₅O₇

Answer 13

Order of balancing equations: C, H, O

There are 9 carbon atoms on the LHS of the equation so there needs to be 3 molecules of CO₂ to make sure there are also 9 carbon atoms on the RHS.

C₆H₈O₇ + 3NaHCO₃ → 3CO₂ +3H₂O + Na₃C₆H₅O₇

Question 14

Why should you put the lid on the container during a paper chromatography experiment?

Answer 14

A lid helps stop the solvent from evaporating

Question 15

True or false? When substances are combined ina mixture their chemical properties change.

Answer 15

False. The chemical properties of the substances in a mixture are unchanged

Question 16

What is a solvent front?

Answer 16

The point that the solvent in paper chromatography reaches as it moves up the paper

Question 17

What is a mixture?

Answer 17

A mixture consists of two or more elements or compounds that are combined, but not chemically bonded together.

Question 18

Explain why techniques to seperate mixtures are described as physical processes.

Answer 18

the seperation of a mixture is a physical process because it does nt involve any chemical reactions, and no new substances are made.

Question 19

Stephen is doing a paper chromatography experiment. He uses a pen to draw a line near the bottom of the filter paper. Why is this wrong?

Answer 19

The line should be drawn in pencil- pen contains ink that dissolves in the solvent.

Question 20

Explain how paper chromatography could be used to seperate a misture containing three different dyes.

Answer 20

• Put a dot of the mixture on the pencil line and place the filter paper in the solvent. - the solvent should be below the pencil line
• Each different dye in the mixture will move up the paper at a different rate, seperating out the dyes.
• You’ll end up with three seperate spots on the chromatogram.

Question 21

When can filtration be used to seperate a mixture?

Answer 21

Filtration can be used when you have a mixture of an insoluble solid and a liquid.

Question 22

When is crystallistion used to seperate a mixture?

Answer 22

Crystallisation can be used to seperate a soluble solid from a solution.

Question 23

Explain how filtration works.

Answer 23

Filtration works by passing a mixture through a filter. The liquid passes straight through but the insoluble solid particles are caught by the filter.

Question 24

Why might crystallisation be used instead of evaporation?

Answer 24

Crystallisation is used if the salt will decompose when heated, or if you want to make big crystals of the salt.

Question 25

What equipment would you need to carry out crystallisation?

Answer 25

To carry out crystallisation you’d need an evaporating dish and a heat source. And once you’ve got you’re crystals they’ll need to be filtered out of the solution, so you’ll need a beaker or flask, funnel and some filter paper.

Question 26

Explain how filtration and crystallisation can be used to seperate a mixture of sand and salt.

Answer 26

Salt is soluble in water, where as sand is not. If water is added the salt will dissolve.The mixture can then be filtered to remove the insoluble sand. Then crystallisation can be used to seperate the salt from the water.

Question 27

In fractional distillation, where is the hottest part of the fractioning column?

Answer 27

the bottom is the hottest part of a fractional distillation column.

Question 28

What sort of mixture can a fractional distillation column be used to seperate?

Answer 28

Mixtures of liquids, inlcuding those with similar boiling points.

Question 29

Explain why simple distillation can’t be used to seperate substances with similar boiling points.

Answer 29

If the boiling points of the compounds are too close together, they will evaporate and mix together again.

Question 30

What is the name of the apparatus labelled B on the diagram below?

What is it used for in this setup?

Answer 30

It’s a condensor. It cools the vapour and turns it back into a liquid, so it can be collected.

Question 31

Cyclohexane, cyclopentane and acetone have boiling points of 81ºC, 49ºC and 56ºC respectively.Describe how you could use a fractional distillation column to seperate a mixture of these compounds.

Answer 31

Prepare a set up with a flask placed below a fractionating column, which is connected to a condenser and has a thermometer on the top. Pour the mixture into the flask and heat it to a temperature between 49ºC and 56ºC , so the cyclopentane evaporates but the other two compounds remain in the flask as liquids. The cyclopentane travels up the fractionating column and into the condenser, where it turns back into a liquid which can be collected. Then increase the temperature to between 56ºC and 81ºC, so the acetone evaporates. It can be collected in a different container. The cyclohexane is left in the flask.

Question 32

True or false. Electrons were discovered before protons or neutrons.

Answer 32

True. The discovery of the electron led to the plum pudding model. Protons and neutrons weren’t discovered until much later, after the nuclear model had been proposed.

Question 33

What was the plum pudding model of the atom?

Answer 33

The plum pudding model descibed atoms as balls of positive charge with electrons embedded in them.

Question 34

Which model replaced the plum pudding model?

Answer 34

The nuclear model replaced the plum pudding model.

Question 35

Describe how alpha particles were used to disprove the plum pudding model.

Answer 35

Alpha particals were fired at a thin sheet of gold. Most of the particles went straight through the sheet, but some were deflected more than expected and a small number were even deflected backwards.. This meant that the positive charge could not be spread out evenly within the atoms, as described by the plum pudding model.

Question 36

How did James Chadwick contribute to our understanding our the atom?

Answer 36

James Chadwick provided evidence for the existence of neutrons within the nuclei of atoms.

Question 37

What did Niels Bohr suggest about the arrangement and movement of electrons in an atom?

Answer 37

Bohr suggested that electrons orbit the nucleus in shells that are a fixed distance from the nucleus. His theory suggested that electrons can only be found in these shells (and not in between them).

Question 38

Tur or false? in an atom, the highest energy levels are filled by electrons first.

Answer 38

False. The lowest energy levels are always filled first.

Question 39

How many electrons are required to fill the first electron shell in an atom?

What is the maximum number of electrons that can go in the second electron shell in an atom?

Answer 39

first shell: 2

second shell: 8

Question 40

What is the electronic structure of the atom below?

Answer 40

The atom has two electrons in it’s first shell, then 5 electrons in it’s second shell. so the electronic structure is 2,5

Question 41

The atomic number of oxygen is 8. what is the electronic structure of oxygen?

Answer 41

Oxygen’s atomic number is 8 so it has 8 protons and 8 electrons. 2 electrons will fill the first shell and the remaining 6 will fill the second shell. The electronic strusture is 2,6

Question 42

Magnesium has 12 electrons. Does it have a partially filled outer shell? Explain your answer.

Answer 42

Magneium has 12 electrons. the first two electrons will fill the first shell and the next 8 will fill the second shell. This leaves two electrons on the third shell, so it is partially filled.

Question 43

How were elements arranged in the first periodic tables?

Answer 43

By relative atomic mass

Question 44

True or false? Mendeleev considered the properties of isotopes when constructing his periodic table.

Answer 44

False. The existence of isotopes wasn’t discovered until later (but they oroved Mendeleev was right to consider the properties of elements as well as relative atomic mass when ordering elements in his periodic table).

Question 45

What is the name for the vertical columns in the periodic table?

Answer 45

groups

Question 46

Explain why thhe way elements are ordered in the modern periodic table is more useful than they were ordered in the first periodic tables?

Answer 46

In the modern periodic table, elements are ordered by atomic number instead of relative atomic mass. This takes into account the existence of isotopes, and means elelments end up in the same group as other elements with similar properties.

Question 47

Why do elements in the same column of the periodic table have properties?

Answer 47

Elements in the same group have the same number of electrons in their outer shell.

Question 48

Calcium is in the second column and fourth row of the periodic table. How many occupied eletron shells does calcium have? How many electrons are in calciums outer shell?

Answer 48

Calcium is in the fourth row (period) of the periodic table, so it has four shells containing electrons. calcium is in the second column (group), so it has two electrons in it’s outer shell.

Question 49

What is a metal?

Answer 49

Metals are elements that form positive ions.

Question 50

Where in the periodic table are metals found?

Answer 50

Metals are found at the bottom and left of the periodic table.

Question 51

Describe the general properties of metals.

Answer 51

Metals are strong, malleable, good conductors of heat and electricity and have high melting and boiling points.

Question 52

Explain why most metals have similar physical properties.

Answer 52

All metals have metallic bonding, which causes them to have similar physical properties.

Question 53

Bill and lucy are arguing about non-metals. Bill thinks non-mteals readily form positive ions. Lucy thinks it is difficut for non-metals to form positive ions. Who is right? Explain your answer.

Answer 53

Lucy is right. Non-metals are found towards the right and top of the periodic table. They have lots of electrons that would have to be removed to give them a full outer shell, and therefore a stable positive ion. The elements towards the top of the periodic table also have their outer shells close to the nucleus. This means they are strongly attracted, so it requires a lot of energy to remove them.

Question 54

Why is it easy for atoms towards the bottom of the periodic table to lose electrons?

Answer 54

Elements at the bottom of the periodic table have more shells of electrons than elements at the top, so their outer electrons are further from the nucleus. Because of this, the outer electrons feel a weaker attraction and are more easily lost.

Question 55

Where are transition metals found on the periodic table?

Answer 55

Transition metals are found in the centre of the periodic table.

Question 56

Name the transition metals.

Answer 56

Cr, Mn, Fe, Co, Ni and Cu

Question 57

True or false. Transition metals are less reactive than Group 1 metals.

Answer 57

True. Group 1 metals will react much more vigorously with water, oxygen or group 7 elements.

Question 58

How do the melting points and densities of group transition metals compare to the melting ponts and densities of group 1 metals?

Answer 58

Transition metals are much more dense than group 1 metals. Thay also have much higher melting and boiling points.

Question 59

Which property of transition metals is demonstrated by the use of the iron in the Haber process?

Answer 59

Transition metals make good catalysts. An iron catalyst is used in the Haber process to speed up the reaction.

Question 60

What are the two other properties of transition metals that aren’t exhibited by Group 1 metals?e.g.

Answer 60

transition metals can form more than one ion. They also form colourful compounds.

Question 61

How are the elements in group 1 of the periodic table more commonly known?

Answer 61

The alkali metals

Question 62

True or false? Group 1 metals are soft.

Answer 62

Alkali metals are soft with low densities.

Question 63

Whay do the elements in group 1 share similar properties?

Answer 63

The elements in group 1 all have one electron on their outer shell/ all form 1+ ions, giving them similar properties.

Question 64

The melting point in ºC of some group 1 metals are: lithium (180.5), sodium (97.8), rubidium (39.5). Predict the melting point of potassium.

Answer 64

Any value between 39.5ºC and 97.8ºC is a good answer (the real answer is 63.5ºC). The melting points of the alkali metals decrease down the group.

Question 65

What is the trend in reactivity down group 1? Explain your answer.

Answer 65

The reactivity of the group 1 metals increases as you go down the group. This is because the outer electron is further from the nucleus, so is less attracted and more easily lost.

Question 66

What might you observe in the reaction between potassium and water?

Answer 66

e.g. potassium reacts vigorously with water. Hydrogen gas is produced during the reaction, so there would be fizzing/bubbling. The energy given out is high enough that the potassium melts and the hydrogen can be ignited, so a flae would also be seen.

Question 67

What are the products when sodium reacts with oxygen?

Answer 67

Sodium reats wth oxygen to form sodium oxide (Na₂O) and sodium peroxide (Na₂O₂).

Question 68

What is the order of the group one elements from top to bottom?

Answer 68

Li

Na

K

Rb

Cs

Fr

Question 69

What sort of compounds do halogens form with other non- metals?

Answer 69

Halogens react with other non-metals to form simple molecular compounds. These compounds contain covalent bonds (shared pair of electrons).

Question 70

What is the charge on a halide ion?

Answer 70

Halogen atoms need to gain one electron to complete their outer shell. So they form 1- ions.

Question 71

Chlorine is a gas at 25ºC. Predict the state of florine at 25ºC. Explain your answer.

Answer 71

As you go down group 7 the boiling points (and melting points) of the halogens increase. Florine is above chlorine so it has a lower boiling point. So florine must be a gas.

Question 72

Describe the trend in reactivity down group 7. Explain your answer.

Answer 72

The reactivity of the halogens decreases down group 7, because the outer shell becomes further from the nucleus.So there’s less attraction and it’s harder to gain an electron.

Question 73

Will chlorine displace bromine from a solution of potassium bromide? Explain your answer.

Answer 73

Chlorine will displace chlorine from a solution of potassium bromide, because chlorine is more reactive than bromine. More reactive halogens displace other halogens from solutions of their salts.

Question 74

Order of the halogens from top to bottom?

Answer 74

Fl

Cl

Br

I

Question 75

How many electrons does helium have in it’s outer shell?

Answer 75

Helium has two electrons in it’s outer shell. ( It’s still full though because the first shell only needs two electrons to be filled.)

Question 76

What is the order of the group 0 elements?

Answer 76

He

Ne

Ar

Kr

Xe

Rn

Question 77

How many electrons do the other noble gases, apart from helium, have in their outer shells?

Answer 77

The rest of the noble gases have 8 electrons in their outer shells.

Question 78

Does kryton have a higher or lower boiling point than argon? Explain your reasoning.

Answer 78

Kyrpton has a higher boiling point than argon. Krypton is below argon in group 0, and the boiling points of the noble gases increase as you go down the group. This is because the relative atomic mass (and number of electrons) increases so there are greater intermolecular forces between the atoms which need to be overcome.

Question 79

Explain why the noble gases are inert (dont react).

Answer 79

The noble gases are inert because they have full outer shells, so don’t need to lose or gain electrons to become stable.

Question 80

The group zero elements exist as monotomic gases. What does this mean?

Answer 80

The noble gases exist as single atoms, not bondede to each other.

Question 81

Would xenon make a good fuel? Explain your answer.

Answer 81

The noble gases are inert so they are non-fammable so xenon would make a poor fuel.