atomic structure-c1

Question 1

What is an atom?

Answer 1

It is the smallest part of an element that can exist

Question 2

What is an element?

Answer 2

An element is a substance made up of the same type of atom

Question 3

What are compunds?

Answer 3

Compounds are substances formed from two or more elements

Question 4

List some facts about the nucleus of the atom?

Answer 4

• It is in the middle of the atom
• It contains protons and neurons
• It has a positive charge because of the protons
• Almost the whole mass is concentrated at the nucleus

Question 5

Some facts about electrons?

Answer 5

• Move around the nucleus in electron shells

- They are negatively charged and tiny, bu they cover a lot of space

Question 6

What is the relative charge and relative mass of a proton

Answer 6

+1 is the charge and 1 is the relative mass

Question 7

What is the relative charge and mass on a neutron?

Answer 7

0 is the charge and 1 is the relative mass

Question 8

What is the relative charge and relative mass on a electron?

Answer 8

-1 is charge and the mass is very small

Question 9

What charge do atoms have and why ?

Answer 9

Atoms are neutral and have no overall charge because they contain the same number of protons as electrons, so the opposite charges cancel out.

Question 10

What does the atomic number tell you?

Answer 10

How many protons there are , it is the bottom number(or the smallest number)

Question 11

What does the mass number tell you?

Answer 11

The total number of protons and neutrons in the atom .

Question 12

What is the law of conservation of mass?

Answer 12

The total mass of the products formed in a reaction is equal to the total mass of the reactants.

Question 13

What is a mixture?

Answer 13

A mixture is made up of two or more substances that are not chemically combined together.

Question 14

What are the differences between a compound and mixture?

Answer 14

Compounds have a fixed composition. Mixtures have no fixed compositions.
Chemical reactions must be used to separate the elements in a compound. In a mixture the different elements or compounds can be easily separated
In compounds there are chemical bonds between atoms of the different elements in the compound. In mixtures there are no chemical bonds between atoms of the different substances in the mixture.

Question 15

What are the physical separation techniques used to separate a mixture?

Answer 15

• filtration
• crystallization
• distillation
• fractional distillation
• chromatography
• evaporation

Question 16

Explain filtration?

Answer 16

The sand that you collect on the filter paper can be washed with distilled water to remove any salt solution left in it. The wet sand is finally dried in a warm oven to evaporate any water off and leave pure,dry sand.

Question 17

What is filtration?

Answer 17

Filtration separates insoluble solids from liquids

Question 18

Explain evaporation?

Answer 18

Pour the solution into an evaporating dish
Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually crystals will start to form
Keep heating the evaporating dish until all you have left are dry crystals.
Evaporation is a really quick way, but you can only use it if the salt doesn’t break down when it is heated, otherwise you will have to use crystallization.

Question 19

Explain crystallization?

Answer 19

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.
Once some of the solution 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.
The salt should start to form crystals as it becomes insoluble in the cold, high concentrated solution
Filter the crystals out of the solution, and leave them in a warm place to dry.

Question 20

How can you separate rock salt?

Answer 20

Grind the mixture to make sure the salt crystals are small, so will dissolve easily.
Put the mixture in water and stir. The salt will dissolve, but the sand won’t
Filter the mixture, the sand will remain on the filter paper and the salt will pass through.
Evaporate the water from the salt so that it forms dry crystals(you could also use crystallisation)

Question 21

When is distillation used?

Answer 21

Distillation is used to separate mixtures which contain liquids

Question 22

Explain simple distillation?

Answer 22

Simple distillation is used for separating out a liquid from a solution.
The solution is heated. The part of the solution that has the lowest boiling point evaporates first. The vapour is then cooled, condenses and is collected.
The rest of the solution is left behind in the flask

Question 23

An example of simple distillation?

Answer 23

You can use simple distillation to get pure water from seawater. The water evaporates and is condensed and collected. Eventually you will end up with just salt left in the flask.

Question 24

What is the problem of simple distillation?

Answer 24

You can only use it to separate things with very different boiling points because if the temperature goes higher than the boiling point of a substance with the higher boiling point, they will mix again.

Question 25

What is fractional distillastion?

Answer 25

Fractional distillation is used to seperate a mixture of liquids even if their boiling points are close together. An example is crude oil

Question 26

Explain fractional distillation? method

Answer 26

You put your mixture in a flask and stick a fracionating column on top. Then you heat it. The different lquids will all have different boiling points- so they will evaporate at different temperatures. The liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column. Liquids with the 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. \When the first liquid has been collected, you raise the temperature until the next one reaches the top.

Question 27

What is chromatography?

Answer 27

Used to separate different dyes in an ink

Question 28

Explain chromatography? method

Answer 28

Draw a line near the bottom of a sheet of filter paper(use a pencil to do this as pencil marks are insoluble) Add a spot of ink to the line and place the sheet in a beaker of solvent e.g water. Make sure it isn't touching the solvent- you don't want it to dissolve into it. Place a lid on top of the container to stop the solvent evaporating. The solvent seeps up the paper carrying the ink with it 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. If any of the dyes in the ink are insoluble(won't dissolve) in the solvent, they will stay on the baseline. When the solvent has nearly reached the top of the paper, take the paper out of the beaker and leave it to dry. The end result is a pattern of spots called a chromatogram.

Question 29

How has the atomic theory changed over time?

Answer 29

At the start of the 19th century John Dalton described as solid spheres, and said that different spheres made up the different elements. In 1897 JJ Thomson concluded from his experiments that atoms weren't solid spheres. His measurements of charge and mass showed that an atom must contain even smaller, negatively charged particles-electrons. The new theory was known as the plum- pudding model. The plum pudding model showed the atom as a ball of positive charge with electrons stuck in it.

Question 30

Explain the alpha scattering experiments?

Answer 30

In 1909 Ernest Rutherford and his student Ernest Masrden conducted the famous alpha scattering experiments. They fired positively charged alpha particles at an extremely thin sheet of gold. From the plum pudding model, they were expecting the particles to pass straight through the sheet or to be slightly deflected at most. This was because the positive charge of each atom was thought to be very spread out through the 'pudding' of the atom. But whilst most of the particles did go straight through the gold sheet, some were deflected more than expected, and a small number were deflected backwards. So the plum pudding couldn't be right. So Rutherford came up with the nuclear model of the atom. In this, there is a tiny positive nucleus at the center, where most of the mass is concentrated. A cloud of negative electrons surrounds this nucleus -so most of the atom is empty space. When alpha particles came near concentrated, positive charge of the nucleus, they were deflected. If they were fired directly at the nucleus, they were deflected backwards. Otherwise, they passed through the empty space.

Question 31

What is Bohr's nuclear model?

Answer 31

Scientists realised that electrons in a cloud around the nucleus of an atom, as Rutherford described would be attracted to the nucleus, causing the atom to collapse. Niels Bohr's nuclear model suggested that all electrons were contained in shells. Bohr proposed that electrons orbit the nucleus in fixed shells and aren't anywhere in between. Each shell is a fixed distance from the nucleus. Bohr's theory of atomic structure was supported by many experiments and it helped to explain lots of other scientists' observations at that time.

Question 32

What did James Chadwick do?

Answer 32

James Chadwick carried out an experiment which provided evidence for neutral particles in the nucleus. These became known as neutrons. The discovery of neutrons resulted in a model of the atom which was pretty close to the modern day accepted version, known as the nuclear model.

Question 33

What are isotopes?

Answer 33

Different forms of the same element, which have the same number of protons but a different number of neutrons. So isotopes have the same atomic number but different mass numbers, examples include carbon-12 and carbon-13.

Question 34

What is relative atomic mass?

Answer 34

Relative atomic mass is an average mass taking into account the different masses and abundances of all isotopes that make up the element.

Question 35

What is the formula to work out relative atomic mass of an element?

Answer 35

relative atomic mass=sum of(isotope abundance times isotope mass number)/ sum of all abundances of all isotopes.

Question 36

Copper has two stable isotopes. Cu-63 has an abundance of 69.2% and Cu-65 has an abundance of 30.8%. Calculate the relative atomic mass of copper to 1dp.

Answer 36

63.6 | if you idk how to do it go look in the revision guide, bottom of page 18 bc i cba to explain