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Chemistry > C1: Atomic structure and the periodic table > Flashcards

C1: Atomic structure and the periodic table Flashcards

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1
Q

What is an atom

A

An atom is the smallest part of an element

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2
Q

What is the radius of an atom?

A

1 x 10 to the power of -10

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3
Q

What is the radius of the nucleus of the atom?

A

1 x 10 to the power of -14

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4
Q

What is an element

A

An element is only made up of 1 type of atom
There are about 100 different elements. Elements are shown in the periodic table.

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5
Q

Why is an atom neutral?

A

In an atom, the number of electrons is equal to the number of protons in the nucleus so the positive and negative charges cancel out
Atoms have no overall electrical charge.

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6
Q

Whats the atomic number?

A

The number of protons in an atom of an element is its atomic number.

All atoms of a particular element have the same number of protons.

Atoms of different elements have different numbers of protons

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7
Q

What is an ion?

A

An ion is an atom that has lost or gained an electron in order to become charged and have a full outer shell so it is stable like a noble gas

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8
Q

What is an isotope?

A

An isotope is an atom of an element that has the same number of protons but a different number of neutrons
E.g Carbon 12 and Carbon 13

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9
Q

What is a compound?

A

Compounds contain two or more different elements chemically combined together in fixed proportions and they are held together by chemical bonds

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10
Q

How are compounds represented?

A

They can be represented by formulae using the symbols of the atoms from which they were formed.

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11
Q

How are compounds formed and seperated?

A

Compounds are formed from elements by chemical reactions.
Chemical reactions always involve the formation of one or more new substances, and often involve a detectable energy change
To separate a compound you need to use a chemical reaction

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12
Q

What is a mixture?

A

A mixture is a substance of two or more different elements or compounds not chemically combined together

The chemical properties of each substance in a mixture is unchanged

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13
Q

How are mixtures seperated?

A

Mixtures are separated by physical separation techniques
These physical processes do not involve chemical reactions and no new substances are made.

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14
Q

Whats the relative atomic mass number?

A

The relative atomic mass number is the average mass taking into account the different masses of isotopes that make up the element and how abundant the isotope is

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15
Q

How do you calculate relative atomic mass?

A

Relative atomic mass(Ar) =
sum of (isotope abundance x isotope mass number)
divided/ sum of abundance of all isotopes.

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16
Q

What is filtration used for?

A

Filtration is used to separate an insoluble solid from a liquid(solution)

17
Q

Describe how you would carry out filtration

A
  1. A filter paper is placed in the filter funnel over a beaker
  2. A mixture of insoluble solid and liquid is poured into the funnel
  3. Make sure none of the liquid goes over the top or down the sides of the filter paper.
  4. The filter paper will only allow some particles to go through which is known as the filtrate
  5. Some particles are too large so will not be able to pass through the filter paper and this is known as the residue
18
Q

What is crystallisation used for?

A

Separating soluble solids from a liquid(solution)

19
Q

Describe how you would carry out evaporation?

A
  1. Place the solution into an evaporating dish
  2. Place the evaporating dish on top of a tripod and gauze and place a Bunsen burner underneath
  3. Slowly heat the solution.The solvent will evaporate and the solution will get more concentrated.Eventually the solid will start to form
  4. Keep heating the evaporating dish until all you have left is the solid
20
Q

Why is crystallisation better than evaporation?

A

Crystallisation takes more time than evaporation but it can produce crystals that would have been decomposed if heated.

21
Q

Describe how you would carry out crystallisation?

A

1.Place the evaporating dish on top of a tripod and gauze mat.Place the bunsen burner underneath the tripod

2.Pour the solution into the evaporating dish and gently heat it. Some solvent will evaporate and the solution will get more concentrated

  1. Once some of the solvent has evaporated or when you see crystals start to form , remove the dish from the heat and leave the solutions to cool
  2. The salt should start to form crystals as it becomes insoluble in the cold concentrated solution
  3. Filter the crystals out of the solution and leave it in a warm place to dry.
  4. You could also dry using an oven or desiccator
22
Q

Rock salt is mainly found as a mixture of salt and sand
Salt and sand are both compounds , but dissolves in water and sand doesn’t
The vital difference in their physical properties means that they can easily be separated.

Describe the method to do this

A
  1. Grind the mixture to make sure that the salt crystals are small , so will dissolve easily
  2. Put the mixture in water and and stir.The alt will dissolve but the sand wont.Heating the mixture will help dissolve the salt
  3. Filter the mixture .The grains of sand won’t fit through the filter paper but the salt solution will
  4. Evaporate or crystalise the water from the salt so it forms dry salt
23
Q

What is distillation used for

A

Distillation is used to separate a solvent from a soluble solid in a mixture with boiling points significantly apart from eachother

24
Q

What do you do in distillation?(2 marks)

A
  1. First we evaporate the liquid by heating
  2. Then we condense the liquid by cooling
25
Q
A
  1. Place the solution with the liquid and dissolved solid in a flask
  2. The flask is connected to a continuous glass tube
  3. The glass tube is surrounded by a condenser.Continuous cold water runs through condenser.This keeps the internal glass tube cold
  4. There is also a thermometre as part of the apparatus
26
Q

describe distil

A
  1. Set up the apparatus and gently heat the mixture
  2. The component of the mixture at the lowest boiling point will evaporate
  3. As the vapour rises it passes into the condenser where it condenses and cools and turned back into a liquid
  4. It is collected in a beaker below the condenser
  5. Components of the mixture with higher boiling points are left behind in the flask
27
Q

What can simple distillation be used for and why isn’t it used for that purpose

A

Simple distillation can be used to make drinking water from sea water.
This requires a lot of energy and is expensive

28
Q

Why does simple distillation not always work?

A

Simple distillation can be used to separate substances with boiling points significantly apart from each other
But if the boiling points of the substances are close then simple distillation does not work
The temperature may rise above the boiling point of more than one of the substance and they’ll end up mixing together

29
Q

What is fractional distillation used for?

A

Fractional distillation is used to separate a mixture of liquids with similar boiling points

30
Q

Describe the method for fractional distillation

A

1.Set up the apparatus

  1. Place the mixture in a flask and attach a fractionating column on the top and heat it
  2. The different liquids will all evaporate at different boiling points - so they will evaporate at different temperatures
  3. The liquid with the lowest boiling point will evaporate first .
  4. When the temperature of the thermometer matches the boiling point of this liquid , its vapour has reached the top of the column and passed into the condenser
    It will then cool and condense and run out the end
  5. The pure liquid can be collected
  6. Liquids at higher boiling points might also start to evaporate .But the column is coller towards the top .So they will only get part of the way up before condensing and running back down the flask
  7. When the first liquid has been collected , you raise the temperature to the next boiling point of the liquids in the mixture.
31
Q

What causes scientific experiments being changed or replaced

A

New experimental evidence may lead to a scientific model being changed or replaced.

32
Q

Before the discovery of the electron what did John Dalton’s theory state

A

John Dalton suggested that atoms were tiny spheres and that different spheres made up different elements and that they could not be divided

33
Q

What did J.J Thomson plum pudding model state

A

The plum pudding model stated that atom was a ball of positive charge with electrons randomly embedded inside

34
Q

What happened in the Alpha scattering experiment?

A

Scientists used a thin sheet of gold foil because you can hammer gold out into a very thin sheet
They then fired tiny positively charged alpha particles at the gold foil

35
Q

What was the results of the Alpha scattering experiment and what did it lead to?

A

The results from the alpha particle scattering experiment led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged.
This nuclear model replaced the plum pudding model.

36
Q

What were the conclusions from the alpha scattering experiment?

A
  1. Most of the alpha particles went straight through the gold foil therefore an atom was mainly empty space so the plum pudding model was wrong
  2. Some of the alpha particles were deflected and changed direction therefore the centre of the atom must have a positive charge that repelled the alpha particles.
  3. One of the alpha particles bounced straight back so the mass of the atom was concentrated in the centre called the nucleus
37
Q

Whats the difference between the plum pudding model of the atom and the nuclear model of the atom

A
  1. In the nuclear model mass is concentrated at the centre in the nucleus
  2. In the plum pudding model mass is evenly distributed
  3. In the nuclear model the positive charge occupies only the nucleus and a small part of the atom
  4. In the plum pudding model positive charge spread throughout the atom
  5. In the nuclear model electrons orbit some distance from the centre and nucleus
  6. In the plum pudding models electrons are randomly embedded in the mass of positive charge
  7. In the nuclear model the atom is mainly empty space

8.In the plum pudding model there is a ‘solid’ mass

Chemistry (3 decks)

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