Atomic Structure and The Periodic Table

Question 1

What is an atom?

Answer 1

Atoms make up all substances and are the smallest part of an element that can exist.

Question 2

What is a compound?

Answer 2

• Compounds contain two or more elements chemically combined in fixed proportions and can be represented by formulae.
• Can only be separated by chemical reactions.

Question 3

What is a mixture?

Answer 3

• Two or more elements or compounds not chemically combined
• Can be separated by: filtration, crystallisation, simple distillation, fractional distillation and chromatography.

Question 4

What is an isotope?

Answer 4

Atoms of the same element with different numbers of neutrons.

Question 5

Relative atomic mass

Answer 5

an average value that takes account of the abundance of the isotopes of the element

Question 6

Relative atomic mass calculations

Answer 6

example: ((isotope 1 mass x abundance) + (isotope 2 mass x abundance)) ÷ 100

Question 7

How is the modern periodic table ordered?

Answer 7

• In order of atomic number
• Elements in the same group have the same amount of electro son their outer shell so they have similar properties

Question 8

John Newland

Answer 8

• In order of atomic mass
• Similar properties occur every eight elements but break after calcium

Question 9

Mendeleev

Answer 9

• Ordered in atomic mass but sometimes switched for atomic weight
• Left gaps for undiscovered elements
• Later knowledge of isotopes explained why order by atomic weight was not always correct

Question 10

Group 1

Answer 10

• React with 02 to make oxide
• React with chlorine to make a white precipitate
• Reactivity increases going down

Question 11

Group 0

Answer 11

Boiling point increases going down

Question 12

Group 7

Answer 12

• They react with metals to form ionic compounds in which the halide ion carries a -1 charge.
• as you go down the group, relative molecular mass, melting point and boiling point all increase
• Reactivity decreases going down

Question 13

Filtration

Answer 13

Filtration:
- Can be used if the product is an insoluble solid that needs to be separated from a liquid reaction mixture
- Can be used in purification

Question 14

Crystallisation: Evaporation

Answer 14

Evaporation:
- Pour the solution into an evaporating dish
- Heat it and the solvent will evaporate
- The solution will become more concentrated until only dry crystals remain.

Question 15

Crystallisation

Answer 15

• Pour the solution into an evaporating dish
• Gently heat it and remove it when the first crystals begin to form
• Leave it to cool and crystals should form as it becomes insoluble in the cool, highly concentrated solution.

Question 16

Simple Distillation

Answer 16

• The solution is heated
• The part with the lowest boiling point evaporates first
• The vapour is cooled and condensed in the condenser and is collected
• The rest is left in the flask

Question 17

Fractional Distillation

Answer 17

• Place a fractioning column at the top of the flask and heat it
• The different liquids have different boiling points
• The liquid with the lowest boiling point evaporates first
• When the temp on the thermometer matches the boiling point, it will reach the top of the column
• Others may also begin to evaporate but the temp is cooler at the top of the column so they will condense and run back down
• Once the first liquid is collected the temp is raised for the second etc.