Periodictity Flashcards
Periodicity
The regular repeating pattern in the properties of elements (chemical and physical)
Ionisation
Losing an electron from the outer shell
First ionisation energy
The energy needed to remove 1 mol of electrons from 1 mol of gaseous atoms of an element to form 1 mol of +1 gaseous ions
halogens
their elemental forms are diatomic molecules
halides
these are monotonic ions with full outer shell
factors affecting ionisation energy
shielding
nuclear charge
atomic radius
1st ionisation energy increases across a period
Nuclear charge increases
shielding by inner electrons stays the same
nuclear attraction of electrons to there nucleus increases
atomic radius decreases (electrons closer)
it takes more energy to remove there first electron
nuclear charge
overall charge of the nucleus
atomic radius
the radius of an atom. we measure this by measuring the distance by the 2 nuclei of touching atoms and
dip between Mg and Al in first ionisation energy
Al has one electron in a higher sub shell (3p) this one of the electrons is removed easier as it is further away from the nucleus therefore the FIE is lower than Mg
dip between P and S in first ionisation energy
S has one 3p orbital that contains a pair of electron. these paired electrons repel each other so one of these electrons are easier to remove therefore S has a lower FIE than P
group 2 first ionisation trends
there is more shielding as you go down the group
nuclear charge increases as you go down the group
atomic radius increases as you go down the group
nuclear attraction between electrons to the nucleus decreases
increased Nuclear charge cancelled out by increased shielding
less energy required to remove outer electron
first ionisation energy decreases down a group
melting points across period 3
Na Mg Al
the charge of the metals increases from +1 to +3
the number of delocalised electrons increases
strength of metallic bond increases
requires more energy to break metallic bond so melting point and boiling point increases
melting points across period 3
Si
Si has a high melting point
have to break strong covalent bonds in order to melt it
this requires a lot of energy
Si is covalently bonded to 4 other Is
melting points across period 3
P S Cl Ar
4 simple molecules
melting point is low
when these substances melt or boil the London forces between the molecules are broken
these are very weak bonds so little energy is required to break them
