Atomic structure and the periodic table

Question 1

What is the difference between a mixture and compound

Answer 1

Mixture - atoms combining with other atoms, not held together by a chemical bond
Compound - atoms combining with other atoms, held together by a chemical bond

Question 2

What is crystallisation used for and how does it work

Answer 2

Produce crystals from a solution

A solution is placed on a basin and heated with a bunsen burner
The liquid dissolves leaving the solid particles behind
This leaves solid crystals

Question 3

What is filtration used for and how does it work

Answer 3

Separates an insoluble solid from a liquid

One beaker has the mixture and another has a funnel with filter paper
Pour the mixture into the funnel
Liquid drips through and the solid stays

Question 4

What is (fractional) distillation used for and how does it work

Answer 4

Separates different liquids from a mixture of liquids
Separates a solvent from a solution

The solution is heated
The evaporated vapour cools and condenses
(The remaining liquid cools and condenses)

Question 5

What is chromatography used for and how does it work

Answer 5

Separates a mixture of soluble substances

Water is poured into a beaker
Paper is lowered into the water and dye spreads up the paper

Question 6

What’s the history of the atom

Answer 6

Dalton thought all matter was made up of tiny particles called atoms
100 years later, Thomson created the plum pudding model when he found out about electrons
In 1909, Rutherford did an experiment where he fired alpha particles at thin gold foil and some particles scattered. He discovered that the atom had a positively charged nucleus at the centre, creating the nuclear model
Bohr discovered that the electron’s orbit the nucleus in shells and that the protons had a small amount of positive charge which was in the nucleus
1932, Chadwick discovered that there were particles in the nucleus which had no charge, this is a neutron

Question 7

What is an isotope

Answer 7

Different forms of the same element which have the same number of protons but a different number of neutrons
Same atomic number but different mass numbers

Question 8

How do you calculate relative atomic mass of an isotope

Answer 8

total mass of atoms / total number of atoms

Question 9

What’s the history of the periodic table

Answer 9

Used to be ordered by relative atomic mass
Early periodic tables were incomplete because of gaps
Mendeleev published his first periodic table in 1869 and arranged it so it increases in atomic weight. He also considered the properties and compounds of elements so there were gaps and elements paired with similar chemical properties were put groups

Question 10

What are the properties of metals

Answer 10

Good conductor of electricity
Good conductors of heat
Shiny
High density
Malleable
Ductile

Question 11

What are the properties of non metals

Answer 11

Poor conductor of electricity
Poor conductor of heat
Dull
Low density
Brittle

Question 12

What are the properties of group 0 elements (noble gases)

Answer 12

Low boiling point
atoms become larger going down
Don’t react with anything

Question 13

What are the properties of group 1 elements (alkali metals)

Answer 13

Soft
Low melting point/boiling point
Increase in reactivity as you go down

When they react with water, it produces hydrogen
When they react with oxygen/chloride, it produces metal oxide/chloride

Question 14

What are the properties of group 7 elements (halogens)

Answer 14

Going down:
The melting/boiling point increases
Molecules become larger