Key Concepts

Question 1

How has the model of the atom progressed over time

Answer 1

Dalton - billiard ball (solid spheres)

Thomson - Plum pudding (positive sphere with negative electrons)

Rutherford - Planetary (negative electrons orbit nucleus in shells)

Question 2

What are the 2 numbers of an element’s symbol

Answer 2

Mass Number (big number):
protons + neutrons (think mass of atom as electrons are so small)

Atomic Number (small number):
number of protons

Question 3

What is an isotope

Answer 3

Atom with same number of protons (so same element) but different number of neutrons

Question 4

What does group and period tell us about an element

Answer 4

Group = number of electrons on outer shell
Period = number of shells

Question 5

What was significant about Mendeleev’s Periodic Table

Answer 5

• gaps left in table as predictions based on characteristics of found elements
• arranged table by atomic mass

Question 6

What do Ionic Compounds form

Answer 6

• Giant Ionic lattice (regular structure)
• Formed through strong electrostatic forces between ions
• Results in high melting/boiling points (great energy needed to overcome forces)

Question 7

How to complete ionic equations

Answer 7

• Separate ionic compounds into ions
• Remove ions that don’t change
• Put ions into equation

Question 8

Forces between covalent molecules vs structures

Answer 8

• covalent molecules = strong intramolecular forces
• covalent structures = weak intermolecular forces (easily overcome so low boiling points)

Question 9

Uses of diamond

Answer 9

• Allotrope of carbon
• Pyramid structure = force applied to one atom is distribute throughout the whole structure
• Therefore very strong
• Can’t conduct electricity, as each carbon atom forms 4 bonds, so no delocalised electrons

Question 10

Uses of graphite

Answer 10

• Allotrope of carbon
• Organised in layers = can slide over one another
• used as a lubricant
• each carbon atom forms 3 bonds, so 1 delocalised electron to conduct electricity