CHEMISTRY 3.4
WORKSHEET ONE
ANSWERS
ATOMS AND IONS
Ionisation Energy
1.
The energy required to remove an electron from one mole of gaseous atoms or
ions.
2.
kJ mol-1
3.
(a)
Na(g) → Na+(g) + e-
(b)
In order to remove electrons from atoms or ions, energy must be
supplied.
(a)
As we remove electrons, the ion becomes successively more positive and
the attractive forces holding the remaining electrons increase. The
greater the force to overcome, the greater the energy required.
(b)
Removing the first three electrons requires them to be all taken from
the third energy level. To remove the 4th electron requires one to be
taken from the full second energy level which is at a significantly higher
energy than the third level.
(c)
Lithium and sodium are both in group one and have only one valence
electron to remove. However sodium has 3 energy levels and so its
valence electron is further from the nucleus than lithium which has only
2 energy levels. This means that sodium’s valence electron is more
easily removed than lithium’s.
(d)
Chlorine has 17 electrons. The graph shows that the first 7 are removed
with steady but small increases in I.E. Then there is a big jump to the
next 8 electrons and another big jump to the last 2. This suggests that
the electrons are arranged in 3 energy levels. 2 electrons in the first
level, 8 in the second level and 7 in the third level.
(e)
Filled and half filled energy levels have extra stability. Be and Mg both
have their valence electrons in a filled s-shell. N and P both have their
valence electrons in a half filled p-subshell.
4.
∆H = +494 kJ mol-1