2.1 periodicity Flashcards
what is periodicity
trends within the periodic table
trend of atomic radius across a period
decreases across a period.
increase number of protons increasing nuclear charge but with the same number of electron shells.
outer electrons are pulled in closer
trend of atomic radius down a group
increases down a group.
number of electron shells increases.
increasing distance between nucleus and electrons reducing the attraction.
more shells, more shielding.
trend of ionisation energy across a period
increases.
number of protons in the same electron shell increases.
nuclear charge increases.
more energy required to remove outer electron.
trend of ionisation energy down a group
decreases.
nuclear charge decreases.
number of shells increase.
less energy needed to remove outer electron
why does Al have a lower ionisation energy than Mg
aluminium loses a 3s electron, magnesium loses a 3p electron.
the p electron is in a higher energy level, so less energy is required to remove it
why does S have a lower ionisation energy than P
sulfur’s outer electron is in a pair, so they will repel each other making it easier to remove one electron
melting point of period 3, between Na and Al
sodium, magnesium and aluminium all contain metallic bonding.
the increase in electrons, increases the metallic bond, increasing melting point across the first 3 elements
melting point of silicone
silicone is a macromolecular compound.
strong covalent bonds, alot of energy needed to break the bonds.
trend in melting point in period 3 of P - Cl
Cl, S, P are simple molecular.
contain weak van der waals.
little energy required to break them.
why does argon have a lower melting point than chlorine
argon exists as monoatomic so has weak van der waals with a full outer shell.
less energy required to break the bonds of Ar than Cl
