1. Atomic Structure and The Periodic table Flashcards
Definition of relative atomic mass
weighted mean mass of an atom of an element compared to 1/12th of the mass of a carbon-12 atom
definition of relative isotopic mass
the mass of an atom of an isotope compared to 1/12th of the mass of a carbon-12 atom
definition of relative molecular/formula mass
average mass of a molecule compared to 1/12th of the mas of a carbon-12 atom
how do you work out relative molecular mass?
add up the atomic mass values of all atoms in the molecule
how do you work out relative formula mass
add up atomic mass for all ions and atoms
how do you work out relative atomic mass from isotopic abundances
- multiple relative isotopic mass by its abundance and add the results together
- divide by 100
what does mass spectrometry show
what samples are made from by looking at their masses
how do you work out the relative atomic mass of different elements
- ,multiple each relative isotopic mass by their abundance and then add together
- divide by the sum of isotopic abundances
how to calculate relative isotopic masses from relative isotopic mass
find the abundance of the missing isotope and substitute into the equation and solve
how to predict the mass spectra for diatomic molecules
- express each percentage as a decimal
- make a table of all possible diatomic molecules
- multiply decimal abundances together
- any molecules with the same product add together
- divide all abundances by the smallest relative abundance getting the smallest whole number ratio
what is an orbital
regions of space where electrons are most likely to be found
subshell notation
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
configuration of chromium and copper
they donate one of their 4s electrons to 3d subshell because its more stable with a full or half full d subshell
first ionisation energy
energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
second ionisation energy
energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
what is periodicity
all elements have the same number of electron shells so there are repeating trends in physical and chemical properties
what decides chemical properties
electron configuration
what happens to atomic radius across a period
it decreases as the postive charge of the nucleus pulls the outer electrons closer
3 factors that affect ionisation energy and how do they affect it
nuclear charge : more protons = more positive = stronger attraction
electron shell : attraction falls with distance. more shells = less attraction
shielding : number of electrons increases = attraction decreases
what happens to ionisation energy across a period
it increases due to stronger nuclear attraction
why does ionisation energy drop between group 2 and 3
group 3 outer electron is in 3p orbital which has a higher energy to it is further from the nucleus and easier to remove
why does ionisation energy drop between group 5 and 6
in phosphorus the electron is removed from a singly occupied orbital. in sulphur it is removed from a pair so it is easier to remove due to repulsion.
metals melting and boiling points across a period
increases as number of delocalised electrons increases which decreases the radius
giant covalent structure melting and boiling points
strongest due to covalent bonds between all the atoms
simple molecular structure melting and boiling points
low due to weak london forces
noble gas melting and boiling points
lowest melting and boiling points as individual atoms (monatomic) have weak london forces
what does isoelectronic mean
have the same number of electrons or same electronic configuration
what is electromagnetic radiation
the energy transmitted as waves with a spectrum of different frequencies
what do emission spectrums show
frequencies of light when electrons drop to lower levels. these appear as coloured lines on a dark background
4 basic principles of the idea of quantum shells
- electrons can only exist in fixed orbitals
- each shell has a fixed energy
- when an electron moves between shells electromagnetic radiation is emitted or absorbed
- because the energy of shells is fixed the radiation will have a fixed frequency
