elements of life Flashcards
what is an elements mass number
the sum of the protons and neutrons
what is an elements atomic number
the number of protons
what is an isotope
atoms of the same element with the same atomic number, but a different number of neutrons, so a different mass number
how to work out number of particles
number of particles = number of moles x avogadro’s number
mole equation for mass
mass = Mr x moles
mole equation for concentration
moles = concentration x volume
mole equation for volume of gases
moles = volume x 24 dm^3
ionic equations
show the ions that are formed in solution and show which particles are reacting
empirical formula definition
the simplest whole number ratio of elements in a compound
empirical formula process
- write out elements
- write out %s as masses
- divide these by element Mr to get number of moles
- divide by smallest number of moles
- multiply all by 2 if a 0.5 value
working out molecular formula process
work out Mr of empirical formula
divide by Mr of molecular formula
use this number to multiple all the atoms in the empirical formula
calculating water of crystallisation
- write out 2 molecules involved
- write out masses of each molecule
- divide these by relative molecular mass to get moles
- divide all of these by the smallest number of moles
percentage yield equation
percentage yield = ( actual yield / theoretical yield ) x 100
measuring the mass of a solid
- Zero the balance
- Place a weighing boat onto balance, add in the solid
- Record the weight of both the weighing boat and solid
- Empty the solid into the container where it will be used
- Reweigh the weighing bottle
- Subtract this mass from the combined weight to find the mass of solid used
measuring volumes of liquid in a volumetric pipette
- Dip the pipette into the solution and use a pipette filler to draw liquid into it
- Stop once the bottom of the meniscus is touching the line on the pipette
- Transfer to the glassware the solution is being transferred to
measuring volumes of liquid with a burette
- Use a funnel to empty the solution into the burette
- Run a small amount into a beaker until there are no air bubbles
- Record the volume to the nearest 0.05 cm3
- Slowly open the tap, letting the solution out until the end point is reached
- At the end point, close the tap and read again to the nearest
0.05 cm3 - Subtract this from the first reading to get the titre
calculating standard solutions
- work out number of moles of solution required
- use number of moles to calculate the mass of the solid
calculating volumes to use when making solutions
volume to use = ( final concentration / initial concentration ) x volume required
acid - base titrations process
- Rinse and fill a burette with the acid
- Measure the start volume
- Fill a 25 cm3 pipette with the alkali solution and empty into a conical flask
- Add 2-3 drops of an indicator
- Run the acid into the flask and swirl the flask until a colour change is seen
- Record the end volume and note this as a trial titration
- Keep repeating this until three titres are reached which are concordant
- Concordant results must be within 0.1 cm3 of each other
- ind the mean of these - the mean titre
indicators to use for acid - base titration
- phenolphthalein
- methyl orange
phenolphthalein indicator
acid = colourless
base = pink
methyl orange indicator
acid = yellow
base = red
what are electrons arranged in
electrons are arranged in energy levels
each electron shell is made up of
subshells
what are the electron subshells
s, p, d, f
what are orbitals
clouds of negative charge that hold electrons
dispersion of electrons within orbitals
two electrons are located in each orbital
dispersion of orbitals within subshells
each subshell has a different number of orbitals
number of electrons in S subshell
2
number of electrons in P subshell
6
number of electrons in D subshell
10
number of electrons in F subshell
14
area of periodic table with S block elements
groups 1 and 2
area of periodic table with D block elements
transition metals
area of periodic table with P block elements
groups 3 to 8
area of periodic table with F block elements
actinides and lanthanides
order of which electron subshells are filled
s, then p, then d, then f
exception: 3d subshell has higher energy than 4s subshell, so 4s subshell is filled before 3d subshell
s orbital shape
sphere
p orbital shape
dumb bell
development of the model of the atom
- Dalton - atoms are small solid spherical particles
- Thomson - plumb pudding model (negative electrons in positive atom), discovery of electron
- Rutherford - discovered positively charged nucleus
- Bohr - electrons were in fixed energy shells
number of orbitals s subshells contain
1 orbital
number of orbitals p subshells contain
3 orbitals
number of orbitals d subshells contain
5 orbitals
number of orbitals f subshells contain
7 orbitals
nuclear fusion definition
the forcing together of 2 light atomic nuclei to make a heavier nuclei, and thus a new element, releasing energy as gamma radiation
nuclear fusion conditions
very high temperature and pressure
electrostatic attraction definition
the attraction between a positive and negative particle
electrostatic repulsion definition
the repulsion between two particles of the same charge