C1 Atomic Structure

Question 1

How were atoms described at the start of the 19th century

Answer 1

Atoms were described as solid spheres by John Dalton.

Question 2

How were atoms described by JJ Thomson in 1897

Answer 2

Described as Plum Pudding Model

Question 3

What is the plum pudding model

Answer 3

Ball of charge with electrons scattered

Question 4

What experiment took place in 1909 and what did it tell us about atoms

Answer 4

Alpha scattering experiment - mass concentrated at the centre, the nucleus is charged. Most of the mass is in the nucleus. Most atoms are empty space. Nuclear model.

Question 5

What did Niels Bohr suggest about atoms in 1911

Answer 5

Electrons are in shells orbiting the nucleus

Question 6

What was discovered about atoms in 1940

Answer 6

James Chadwick discovered neutrons

Question 7

Whats the charge, relative mass and location within the atom of protons

Answer 7

Charge: +1
Relative Mass: 1
Location: Nucleus

Question 8

Whats the charge, relative mass and location within the atom of neutrons

Answer 8

Charge: 0
Relative Mass: 1
Location: Nucleus

Question 9

Whats the charge, relative mass and location within the atom of electons

Answer 9

Charge: -1
Relative Mass: 1/1850
Location: Outside nucleus in shells

Question 10

What is the mass number

Answer 10

The top number next to an element in the periodic table.

It is the number of protons + number of neutrons

Question 11

What is the atomic number

Answer 11

The bottom number next to an element in the periodic table.

It is the number of protons which is the same as the number of electrons

Question 12

What is the structure of an atom

Answer 12

Atoms are composed of a positively charged nucleus made of protons and neutrons surrounded by negatively charged electrons arranged in shells

Question 13

Whats an ion

Answer 13

An ion is a charged atom (or a group of atoms)

Na+, Cl- Charged atoms

SO4^2- Charged group of atoms

Question 14

Why are some ions positive and some negative

Answer 14

Atoms that gain electrons form negative ions. If atoms lose electrons form positive ions.

Oxygen atom: 8p 8n 8e: O
Oxygen ion: 8p 8n 10e: O^2-

Question 15

What are isotopes

Answer 15

Isotopes are atoms of the same element with different numbers of neutrons. They have identical chemical properties, but their physical properties, such as density, can differ.

Question 16

What is the electronic structure of atoms

Answer 16

The 1st electronic shell can hold max. 2 electrons
2nd shell 8
3rd shell 8
4th shell Holds the remainder

Question 17

What does the number of electrons in the outer shell determine

Answer 17

Which group the element is in and determines in which way the element reacts (it’s reactivity).

Question 18

What is the overall charge of an atom

Answer 18

0

Same number of protons as electrons

Question 19

How many times bigger is the radius of an atom compared to the radius of the nucleus

Answer 19

The radius of an atom is around 10,000 times the size of the radius of the nucleus

Question 20

Do compounds always have similar properties to the elements that make it up

Answer 20

No. Compounds often have totally different properties to the original elements

Question 21

Which side of the chemical equation are reactants found

Answer 21

The left

Question 22

What is a compound

Answer 22

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

Question 23

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

Answer 23

A chemical reaction

Question 24

What is a mixture

Answer 24

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

Question 25

Why are techniques to separate mixtures described as physical processes

Answer 25

The separation of a mixture is a physical process because it does not involve any chemical reactions, and no new substances are made.

Question 26

When substances are combined in a mixture, do their chemical properties change.

Answer 26

No. The chemical properties of the substances in a mixture are unchanged

Question 27

How does filtration work

Answer 27

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

Question 28

Why might crystallisation be used instead of evaporation

Answer 28

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

Question 29

When can filtration be used to separate a mixture

Answer 29

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

Question 30

When is crystallisation used to separate a mixture

Answer 30

Crystallisation is used to separate a soluable solid from a solution

Question 31

Why can't simple distillation be used to separate substances with similar boiling points.

Answer 31

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

Question 32

What is the tube in distillation called and what is it used for

Answer 32

Condenser. It cools the vapour and turns it back to liquid, so it can be collected. The cooling water enters at the bottom and exits at the top because when the water heats up it rises and exits at the top.

Question 33

Three liquids with boiling points of 81°C, 49°C and 56°C. How could you use fractional distillation to separate a mixture of these compounds

Answer 33

Heat the gractioning column to 49 to 55 degress so only one liquid evaporates and then condenses to be collected in a flask. Then increase the temperature to 56 to 80 degrees so another liquid evaporates and condenses to be collected in another flask, therefore leaving the final liquid behind.

Question 34

How can paper chromatography be used to separate a mixture containing three different dyes.

Answer 34

Put a dot of the dye mixture on the pencil line and place the filter paper in 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 your chromatogram.

Question 35

Why can't you use a pen to draw a line near the bottom of the filter paper.

Answer 35

It should be drawn in pencil because the pen contains ink which will dissolve in the solvent