Trends in Ionisation Energy Chemistry Tutorial
- Ionization energy is also referred to as ionisation energy.
- Ionization energy is given a number of symbols including I, E, and I.E.
- Ionization energy is measured in kilojoules per mole (kJ mol-1) or electronvolts per atom (eV)1.
- Ionization energy, or ionisation energy, is the energy required to remove an electron from a gaseous atom or ion.
- First Ionization energy is the energy required to remove an electron from the gaseous atom
First Ionization for the element M:
M(g) → M+(g) + e-, first ionization energy is I1
First Ionization for Hydrogen:
H(g) → H+(g) + e-
First Ionization for Carbon:
C(g) → C+(g) + e-
- Second Ionization energy is the energy required to remove an electron from the gaseous ion
Second Ionization of element M:
M+(g) → M2+(g) + e-, second ionization energy is I2
Second Ionization for Carbon:
C+(g) → C2+(g) + e-
- The second ionization energy of an element will be higher than the first ionization energy.
For an element: I2 > I1
- General trends in the ionization energy of elements in the Periodic Table:
⚛ Ionisation energy decreases down a group.
⚛ Ionisation energy increases across a period from left to right.
- Successive ionization energies for an element provide evidence for the number of electrons occupying the highest energy level, or valence shell, of the atom.