definition of the first electron affinity
the enthalpy change when 1 mole of electrons is added to 1 mole of gaseous atoms to form 1 mole of gaseous ions each with a single negative charge under standard conditions
first electron affinity symbol
EA1
standard example equation to show the first electron affinity
X(g) + e– → X–(g)
is EA1 usually exothermic or endothermic
exothermic ( energy is released), negative number
in which case are successive electron affinities used?
where an element accepts more than one electron
what do the 2nd and 3rd electron affinities respresent
the formation of 1mole of of gaseous ions with 2- and 3- charges respectively
are the 2nd and 3rd electron affinities endothermic or exothermic
endothermic (energy is absorbed)
why are the 2nd and 3rd electron affinities endo and not exo?
the incoming electron is being added to an already negative ion
energy is required to overcome the repulsive forces between them
what is the value of the electron affinity depend on
how strongly the incoming electron is attracted to the nucleus
the more energy i released ( more exothermic, more negative) the EA value is, the
greater the attractive forces between the electron and nucleus
the factors affecting the electron affinity of an element are the same as those affecting
ionisation energies
what are ionisation energies for ?
the formation of positive ions via the loss of electrons
3 factors influencing EAs and IEs
nuclear charge
distance from nucleus
shielding between
the greater the nuclear charge, the
stronger the attractive forces between an incoming electron and the nucleus
the greater the distance between the nucleus and outermost shell/orbital where the electron is added, the
weaker the force of attraction
the greater the number of shells, the
greater the shielding effect and the weaker the force of attraction