Key Concepts In Chemistry Flashcards
What does oxidising mean
Allows other materials to burn more fiercely
What does harmful mean
Can cause irritation, reddening or blistering of the skin
What does environmental hazard mean
Harmful to organisms and to the environment
What does highly flammable mean
Catches fire easily
What does toxic mean
Can cause death
What does corrosive mean
Destroys materials
What is a hazard
Anything that has the potential to cause harm or damage
What is a risk
The probability that someone or something being harmed if they are exposed to the hazard
How has the theory of atomic structure changed over time
Early 19th century - Dalton - atoms as solid spheres
1897 - Thomson - plum pudding
1909 - Rutherford - nuclear atom
Later - Bohr - refined model
What is mass number
No. of protons + neutrons
What is atomic number
No. of protons and electrons
How are isotopes different
They have a different no. of neutrons
What is relative atomic mass
The average mass of one atom of the element compared to 1/12th the mass of one atom of C-12
How to work out isotope abundances
Isotopic mass x isotope abundance/ isotopes abundances added
Who made the first periodic table
Dmitri Mendeleev in 1869
What are 3 differences between his periodic table and the current one
- Mendeleev left gaps
- Mendeleev arranged in order of atomic mass
- Didn’t include Noble gases
What is the maximum no. of electrons in each shell
1 - 2
2 - 8
3 - 8
What is an ion
A charge particle
When are ionic bonds formed
When a metal and non-metal react
Properties of ionic compounds
- high melting and boiling point as they are held together by strong electrostatic forces of attraction
- don’t conduct electricity as a a solid
- conduct electricity when liquid or dissolved in water
2D representations
-Show what and how the atoms are connected in a substance
- Doesn’t show the shape of the substance
- Doesn’t show the size of the atoms
Dot and cross
- How the compound is formed
- Don’t show the arrangement
3D models
-Show arrangement of ions
- Only show the outer layer
Ball and Stick
- Good for visualisation
- Leave big gaps between atoms
- Don’t show correct scale for atoms
Properties of simple molecular substances
- Low melting and boiling points as there are weak intermolecular forces
- Don’t conduct electricity
Properties of giant covalent substances
- Strong covalent bonds
- High melting and boiling points
- Generally don’t conduct electricity apart from graphite and graphene
Diamond
- Each Carbon forms 4 covalent bonds
- High melting point
- Lattice structure
- Doesn’t conduct electricity as there are no free electrons
Graphite
- Each Carbon only forms 3 bonds
- Sheets arranged in hexagons
- Layers held together weakly
- Soft and slippery
- High melting point
- Conducts electricity as one delocalised electron
What is graphene
One layer of graphite
What is a fullerene
Molecules of carbon
Uses of fullerenes
Drug delivery around the body
Lubricants
Energy storage
Properties of metals
high boiling points due to strong electrostatic forces of attraction
usually shiny solids at room temperature
malleable as layers can slide over each other
good conductors of electricity and heat
What is the empirical formula
The simplest ratio of atoms
How much does one mole of a substance weigh
Grams of the Mr of that substance
What is avogadro’s number
6.023 x 10^23
Formula for no. of moles
Mass in g/ Mr
Formula for concentration (dm^3)
mass / volume
ALSO
no. / volume
Formula for no. of moles in a gas
volume / 24 (dm^3)
How to work out the empirical formula
Work out no. of moles
Divide by smallest no. to form ratio
What is a limiting reactant
A reactant that stops the reaction when all of it is used up
The amount of product formed is proportional to the amount of reactant
