mercury and bromine are the only elements liquid at
room temperature (25"c)
covalent radius
half the distance between the nuclei of 2
bonded atoms
Increases down the group \
the number of occupied electron shells/energy
levels increases
decreases across the period (left>right)
the nuclear charge is increasing which exerts an
increasing attraction on the outer electrons, resulting in
a decrease in covalent radius
ionisation energy
''the first ionisation energy of an element is
the energy required to remove one mole of
electrons from one mole of gaseous atoms of
an element''
ionisation increases across a period (left to right)>>
positive nuclear charge is increasing so
it is more difficult for the negative
electron to be pulled away
the atoms are getting smaller
and so the negative electron is
closer to the positive nucleus
and attracted more strongly
ionisation energy increases down a group
the outer electron to be removed is in a shell
further away from the nucleus so the atoms are
getting bigger and so the negative electron is
further away from the positive nucleus and
attracted more strongly
there will be a greater screening effect due to more
shells of inner electrons between the outer shell and
the nucleus. These inner electrons are said to
'screen' or 'shield' the electrons in the outer shell
from the positive nucleus
electronegitivity
''electronegativity is a measure of the
attraction an atom has for the electrons in a
bond''