Chapter 1 - Atomic Structure

Question 1

What are all substances made out of?

Answer 1

Atoms.

Question 2

Define an element.

Answer 2

• A substance made from 1 type of atom.

Question 2

Define an element.

Answer 2

• A substance made from 1 type of atom.

Question 3

Define a compound.

Answer 3

• Substances made up of 2 or more types of atom.

Question 4

State the definition of a molecule.

Answer 4

• A substance made up of 2 or more atoms chemically bonded together.

Question 5

Describe the basic structure of the atom.

Answer 5

• Nucleus in the centre made up of neutrons and protons.
• Surrounded by electrons orbiting in shells.

Question 6

What is the Law of Conservation of Mass?

Answer 6

• The total mass of the products formed in the reaction = The total mass of the reactants.

Question 7

Why do chemical equations need to be balanced?

Answer 7

• This is because atoms cannot be created or destroyed in a reaction.

Question 8

Give all 4 of the state symbols used in equations.

Answer 8

(s) - Solid
(l) - Liquid
(g) - Gas
(aq) - Aqueous Solution

Question 9

Balance the equation:

KNO3 —–> KNO2 + O2

Answer 9

2KNO3 ——-> 2KNO2 + O2

Question 10

Balance the equation:

Fe2O3 + CO ——> Fe + CO2

Answer 10

Fe2O3 + 3CO ——-> 2Fe + 3CO2

Question 11

Define the word mixture.

Answer 11

• A mixture is made up of 2 or more substances not chemically combined.

Question 12

Give 4 methods that can be used to separate mixtures.

Answer 12

• Filtration
• Crystallisation
• Distillation
• Chromatography

Question 13

Explain how a student could use distillation to obtain a pure salt and it’s solution from sea water. [4]

Answer 13

• Sea water is heated to evaporate the solvent. [1]
• Water vapour enters liebig condenser. [1]
• Hot vapour is cooled and condensed into a liquid collected in a beaker. [1]
• Pure salt remains in the flask. [1]

Question 14

Explain a method to carry out paper chromatography.

Answer 14

• Use a tube to dab a spot of the solution on a pencil line drawn at the bottom. [1]
• Place the paper standing in a solvent in a beaker. [1]
• Solubility of the components of the mixture determines how far up the paper it will travel. [1]
• The higher the solvent has travelled, the more soluble a substance is. [1]

Question 15

Describe the “Plum Pudding” model by J.J Thomson.

State which sub-atomic particle he discovered.

Answer 15

• Sphere of positive charge with negative electrons dotted around the sphere.
• Electrons.

Question 16

How did Rutherford test Thomson’s plum pudding model?

Answer 16

• He fired positively charged alpha particles at a thin sheet of gold foil. Some particles passed through, but some bounced off in different directions and some rebounded, proving Thomson’s model wrong.

Question 17

Why did Bohr challenge Rutherford’s nuclear model?

Answer 17

• If the nucleus was positive and the electrons in the shells were negative, the whole atom would collapse inwards, proving Rutherford’s model wrong.

Question 18

How do you calculate the number of neutrons in an element?

Answer 18

Number of neutrons = mass number - atomic number.

Question 19

State the relative charges and masses for the 3 sub-atomic particles.

Answer 19

Protons have +1 charge and relative mass of 1
Neutrons have 0 charge and relative mass of 1
Electrons have -1 charge and relative mass of 1/2000

Question 20

What is the atomic number?

Answer 20

• Number of protons in each atom of an element.

Question 21

What is an ion?

Answer 21

• A positive or negative charged atom.

Question 22

What is an isotope?

Answer 22

• Atoms of the same element with different number of neutrons and same number of protons.

Question 23

Sodium (Na) has a mass number of 23 and a atomic number of 11. Work out the number of protons, neutrons and electrons in sodium.

Answer 23

• 11 protons
• (23-11) 12 neutrons
• 11 electrons

Question 24

Explain how electrons can be arranged in shells.

Answer 24

• The 1st shell can hold up to 2 electrons.
• The 2nd and every other shell needed afterwards can hold up to 8 electrons.

Question 25

How does the periodic table influence the number of electrons in the outer shell of an element?

Answer 25

• The group the element belongs to correlates to the number of electrons in the outer shell. (e.g Group 1 elements have 1 electron in their outer shell)

Question 26

How are elements in group 0 different in terms of electronic structure.

State the element that is an exception to this.

Answer 26

• Elements in group 0 have no electrons in their outer shell, meaning they don’t react.
• Helium is an exception, with 2 electrons in it’s outer shell.