periodicity Flashcards
periodicity
trends in repeating patterns across periods
giant structures
high melting/boiling point
strong bonds broken
simple structures
low melting/boiling point
weak bonds broken
first ionisation energy
energy required to remove an electron from each atom in one mole of gaseous atoms to form one mole of gaseous +1 ions
factors affecting ionisation energy
nuclear charge
atomic radius
sheilding effect
trend in ionisation energy down a group
ionisation energy decreases
number of shells increases
greater shielding effect
atomic radius increases
weaker nuclear attraction on outer electrons
requires less energy to remove an electron
trend in ionisation energy across a period
ionisation energy increases
number of shells and shielding effect remain constant
nuclear charge increases
atomic radius decreases
stronger nuclear attraction on outer electrons
requires more energy to remove an electron
how to identify group number from successive ionisation energies
the largest jump in successive ionisation energy shows removal of an electron from a new shell
why ionisation energy increases with increasing ionisation number
proton : electron ratio increases
more nuclear attraction on outer electrons
trend in reactivity of group 2 elements
reactivity increases down group
atomic radius increases
number of shells and shielding effect increases
weaker nuclear attraction on outer electrons
ionisation energy decreases
so less energy is needed to remove the 2 electrons from the outer shell
trend in solubility of group 2 hydroxides
solubility increases down group
trend in thermal decomposition of group 2 carbonates
more difficult to decompose with
heat down the group
uses of group 2 metals
Mg(OH)2 - use as an antacid
Ca(OH)2 - neutralise acidic soil
BaSO4 - visualising in X-rays
trend in melting/boiling point of the halogens
melting/boiling point increases down group
there are more electrons
more induced dipole-dipole forces between molecules
require more energy to overcome
trend in reactivity of the halogens
reactivity decreases down group
number of shells and shielding effect increases
atomic radius increases
weaker nuclear attraction on outer electrons
nucleus is less able to attract another electron into its outer shell
