C1 Flashcards
How big is an atom compared to its nucleus?
100 000 times bigger
Relative mass of electron?
0.0005
Atomic number
Number of protons (electrons as well)
Mass number
Number of protons + neutrons
Isotopes
- Same number of protons
- Different number of neutrons
Ions
Charged particles
- Lost electrons
- Gained electrons
John Dalton Model
- All atoms of elements are identical
- Different elements are different atoms
What did John Thompson do?
Discovered the electron
What model did John Thompson create?
Plum-pudding model:
- atoms are neutral
- atoms contain electrons
- electrons inside positive mass
What did Ernest Rutherford do?
- Launched alpha particles at gold foil
- Some of them went through
- Some of them changed direction
- Some came back
What conclusion did Rutherford come to?
- Nucleus is positive, with huge mass
- Most of atom is empty space
- Electrons orbit nucleus
What did Bohr do?
- Show that there are energy levels
- Where electrons reside in
Problem with particle theory?
- Particles aren’t spheres
- No size of particles specified
- Doesn’t show forces between particles
When did Mendeleev make the first periodic table?
1869
How was the first periodic table?
- Arranged in order of atomic mass
- Elements with similar properties arranged in vertical groups
- Left a few gaps
What did the gaps mean in the periodic table?
- Predicted properties of undiscovered elements
What’s a period (Periodic Table)?
Rows
- Represent new full shell of electrons
What’s a group (Periodic Table)?
Columns
- Similar properties
- Number of electrons in outer shell
Ionic Bond
Metal + Non-metal
Properties of Ionic Compounds
- High melting & boiling points
- Strong electrostatic forces
- Solid can’t conduct electricity, fixed ions
- Liquids can conduct electricity
- Easily dissolve in water
Covalent Bond
Shared pair of electrons
- Non-metal + non-metal
What’re the molecules called that use covalent bond?
Simple Molecules
Covalent bonds are
strong electrostatic attraction.
Bonds between simple molecules are
weak intermolecular forces.
Giant Covalent Structures
- High melting & boiling points
- All atoms are covalently bonded
Giant Covalent Structures examples
- Diamond
- Graphite & Graphene
- Fullerenes
Diamond
- Lustrous & Colourless
- 4 covalent bonds
- Very hard
- Very high melting point
Graphite
- Shiny
- 3 covalent bonds
- Sheets of graphene that can slide over
- Low forces between layers
- High melting point
Why can graphite conduct electricity?
- 3/4 covalent bonds
- delocalized electrons that conduct electricity
Fullerenes
- Large molecules shaped like balls or tubes
- Carbon atoms arranged in rings
- Conduct electricity, delocalized electrons
- Lower melting & boiling points
Nanoparticles
- 1-100 nanometres in size
- Few hundred atoms
- High SA:V ratio
Uses of nanoparticles?
- Catalysts
- Sun creams/Deodorants
- Nanomedicine
- Electric circuits
- Added to material to make it stronger
Polymerisation
Forming of polymers through fusion of monomers at high pressure & temp
Weak & Strong forces
Weak: Intermolecular forces
Strong: Covalent and ionic bonds
Empirical formula
Whole number ratio of atoms in a compound
Metallic bonding
Metal ions + sea of delocalized electrons
Metal properties
- Hard & dense
- Lustrous
- Very strong metallic bonding
- High melting & boiling points
- Malleable
- Conductor of heat & electricity
What happens when metals react with oxygen?
Form metal oxides
Pure substance
Made of of a single element or compound
How can you test the purity of a sample?
Comparing boiling/melting points
- If it’s different than expected, it’s impure
Simple distillation
Separates liquid from solution.
- Heat up solution until liquid evaporates
- Then condense liquid
Fractional Distillation
Separates mixture of liquids
- Different liquids melt at different boiling points
- Heat it up and they will boil at different temps
- Until they’re all separated
Filtration
Separates Insoluble solid from a liquid
- Filter paper in funnel
Crystallisation
Separates soluble solids by crystallisying them
- Gently heat solution
- At point of crystallization, leave to cool
- Salt will from crystals
- Then use filtration
Chromatography
Separate and identify substances in mixture
Mobile phase
Substance that moves up.
E.g. water
Stationary phase
Substances don’t move.
E.g. paper
Rf value
distance travelled by solute / distance travelled by solvent
Gas Chromatography
- Unknown substance injected in tube with stationary phase (thick liquid)
- Substance moves through stationary phase
- Retention time is time it takes to pass through
- This identifies substances
Aqueous
dissolved in water
Where can you only use half equations
Redox Reactions
Mole
amount of substance
Avogadro’s constant
6.022 x10^23
Bond Breaking
Takes in energy (Endothermic)
Bond Forming
Gives out energy (Exothermic)
Energy change
Energy Change = Energy for breaking bonds - Energy for forming bonds
How can you test the pH of a solution?
- Indicator
- Universal Indicator
- pH Probe
Acids
less than 7 pH, forms H+ ions in water
Base
more than 7pH
Alkali
Base that dissolved in water, forming OH- ions in water
What is pH
Concentration of hydrogen ions in a solution, inversely proportional
Indicator
Dye that changes colour when reaches certain pH
Universal Indicator
Combination of dyes, show what pH it’s at.
Neutralisation reaction
Acid + Base –> Salt + Water
What pH is at the end of a neutralization reaction
pH 7
Strong acids
Ionize completely inwater
Weak acids
Do not fully ionize in water
Concentrated acid
How much acid is in liter of water
How does acid concentration change pH
10x concentration = -1 pH
Acid + Metal –> ?
Acid + Metal –> Salt + Hydrogen
Acid + Metal carbonate –> ?
Salt + Water + Carbon dioxide
