Elements Of Life 🌲 Flashcards
What is an isotope?
Same atomic number and a different mass number
What is the plum pudding model?
The cell is a circle with mainly positive charged “pudding” and negative “plums” dotted around
How was the plum pudding model proved wrong?
- alpha particles fired at sheet of gold
- were expecting alpha partciles to be reflected back at odd angles
- went straight through though.
- some went back 90° too
- nucleus in the centre
How was the neutron discovered?
- realisation that nucleus heavier than just protons
- must be other stuff in there
What are relative masses?
Masses of atoms compared to carbon-12
What is a mole?
Amount of a substance
Moles=?
Particles you have/ avogadros constant
Mass/ mr
Conc x volume
Vol/ 24
What is an empirical formula?
The smallest ratio
How do you do water of crystallisation?
- Moles water lost
- How many moles in the anhydrous salts
- Do the ratio: mol anhydrous/ mol water
Percentage yield=
(Actual/ theory) x 100
Vol to use=
(Final conc/ initial conc) x vol required
In an acid/ base titration, when do you know what indicator to use?
Methyl orange= yellow to red when adding acid to alkali
Phenolphthalein= red to colourless when acid to alkali
What is spin pairing?
Electrons in the same orbital spin in opposite directions
What is an ionic bond?
When ions are stuck together by electrostatic attraction.
What behaviours do ions do?
- Conduct electricity
- High MP as strong electrostatic attraction
- Soluble in water as polar
What is a covalent bond?
Shares electrons
Covalent bond properties
Fairly low MP and BP
Cant conduct electricity
Water insoluble
How do properties of ionic lattice provide evidence for covalent bonding?
- high MP
- hard
- good thermal conductivity
- wont dissolve
- cant conduct electricity
What makes the biggest angles and what makes the smallest?
LP/ LP biggest angles
BP/ BP smallest
Tetrahedral bond angle
109.5°
Trigonal pyrimidal
107°
- 1 LP
- 3 BP
Bent shape
- 5°
- 2 LP
- 2 BP
Trigonal planar
120°
- 3 BP
- 0 LP
Trigonal bipyrimidal
120° & 90°
- 5 BP
- 0 LP
Octahedral
90°
- 6 BP
- 0 LP
Periodic trends
- CD increased across the group
- first ionisation enthalpies decrease down the group and increase across a period
What is the first ionisation enthalpy?
Energy needed to remove 1 electron from each atom in 1 mol gaseous atoms to form 1 mole gaseous +ve ions.
What affects the size ionisation enthalpies?
- Electron shielding
- Atomic radius
- Nuclear charge
Group 2 reactions?
- with water to make hydroxides
- burn in oxygen to make oxides
Thermal stability in group 2 carbonates
- increases down the group
- carbonates large anions and can be made unstable by cations
- makes the carbonate polarise itself
- the greater the distortion the less stable the carbonate ion
- large cations = less distortion as they have a lower CD. Larger cations are down the group
What are salts?
Formed from positively charged cations and negative anions so the product is neutral
Solubility rules?
- group 1 and ammonium salts soluble
- nitrates soluble
- group 7 soluble apart from silver halides
- sulphates soluble
- most hydroxides and carbonates insoluble
How do you make insoluble salts?
- Precipitation
- Pick 2 solutions that contain the ions that you need
- Filter
Making soluble salts?
- Pick an acid, plus an insoluble base
- Metal oxide will dissolve as acid reacts.
- Filter out the excess metal
- Evaporation of water
Making soluble salts using an alkali?
- Need to add the correct amount of alkali to neutralise the acid.
- Use a titration
- Use an indicator
- Evaporation of water
What happens when electrons absorb energy
- get excited to a higher energy level
- electrons release energy by dropping from a higher energy level
- energy levels are quantised
What is absorption spectra?
Dark lines coloured background
- E= hv
- electrons only absorb energy with correct frequency for the energy level
- means frequencies of light missing
What is emissions spectra?
Bright lines coloured background
- when electrons drop energy levels frequencies given out
