2 - Atoms, ions and compounds Flashcards
mass within atoms
mass of proton = mass of neutron
electron gas negligible mass
charges within atoms
electron is negative
proton is positive
neutrons has no charge
atoms
protons = electrons
most neutrons = protons
identity of an element
different elements have atoms with the different number of neutrons
what does the atomic number show
number of neutrons in an atoms
-> as well as electron
isotopes
atoms of the same element with different numbers of protons and therefore different atomic masses
- most elements are made of a mixture of isotopes
isotopes and chemical reactions
- different isotopes of the same element have the same number of e-
- the number of neutrons have no effect on the reactions of that element
- so different isotopes of the same element react in the same way chemically
ions
a charged atom, where the number of e- is different to neutron number
what is the atomic mass unit u
the standard mass for atomic mass is 1 u, the mass of 1/12 th of the mass of a carbon atom
- approximately the mass of a proton or electron
relative atomic mass
the weighted mean mass of an atom of an element relative to 1/12th of the mass of carbon-12
relative atomic mass equation
sum (isotopes mass x relative abundance)/ total abundance
copper ions
CU+
Cu2+
Iron ions
Fe 2+
Fe 3+
binary compounds
contains only two elements
ammonium
NH4 +
Hydroxide
OH-
Nitrate
NO3 -
Nitrite
NO2 -
Hydrogencarbonate
HCO3 -
Manganate (VII)
MnO4 -
carbonate
CO3 2-
sulfate
SO4 2-
sulfite
SO3 2-
dichromate (VI)
Cr2O7 2-
phosphate
PO4 3-
amount of substance -n
the number of particles in a substance
how many particles does one mole of a substance contain
avogadro constant 6.02 x 10 ^23
mass of one mole of any atom is
relative atomic mass
equation linking mass mr and moles
n=mass/mr
molecular formula
is the number of atoms of each element in a molecule
empirical formula
simplest whole number ratrio of atoms of each element in a compound
relative molecular mass
the weighted mean mass of a molecule of a compound compared with 1/12 th of the mass of an atom of carbon-12
relative formula mass
the weighted mean mass of the formula unit of a compound compared with 1/12 th of the mass of an atom of carbon-12
two assumptions when finding out the formula of a hydrated salts through experiment
1) all the water has been lost
2) no further decomposition
1dm ^3 =
1000 cm3 = 1000ml = 1litre
moles = of solution
c x V
standard solution
a solution of a known concentration
molar gas volume
volume per mole of gas molecules at stated temp and pressure
what is RTP
20 ‘c and 101kPa
at RTP 1 mole of gas has
volume 24 dm^3
mole of a gas
volume / molar gas volume Vm
must be of same units
if V = dm3 than Vm is 24
if V is cm3 than Vm is 24000
ideal gas equation and units
pV=nRT
p= Pa (kPa -> Pa x10^3)
V= m^3 (cm3 -> m3 x10^-6) or (dm3 -> m3 x10^-3)
T= K (‘C -> K +273)
theoretical yield
why is this not always possible
maximum possible amount of product
- reaction may not have gone to completion
- other reactions may have taken place (side reactions)
- purification of the product may result in los of the product
percentage yield
=actual yield / theoretical yield x 100
limiting reagent
the reactant that is not in excess
it is completely used up
atom economy
- how well the atoms have been utilised
= (sum of molar mass of desired products)/sum of molar mass of all products x 100
reactions with high atom economies
- produce a large proportion of desired products and few unwanted waste products
-make best use of natural resources
why is atom economy not always the best way to see if a reaction is sustainable
- may use reactants that are sourced wrongly
- other reactions can have a poor percentage yield but high atom economy
