Ionization Energy
Ionization energy refers to the minimum amount of energy that is needed when removing an electron from the outermost energy level of an atom to form a cation. The element in question must be in the gaseous state (Ash, 2005, 70). It is also defined as the minimum amount of energy required when removing the most loosely attached electrons from the outermost energy level of an electron. Depending on the number of valent electrons for the element that is ionizing, we have first ionization energy when losing only one valent electron, second ionization energy when removing the second valent electron, and third ionization energy when removing the third electron for trivalent elements (Sharpe, 2008, 44).
First and Second Ionization Energy
The first ionization energy can be referred to as the amount of energy that is used to remove the first valent electron from the outermost energy level of an atom in gaseous state. The second IE is the amount of energy that is used to remove the 2nd electron from a positive ion since the atom had already lost 1 electron where the first ionization energy was used. The first ionization energy is always less as compared to the second ionization energy. More energy is required when removing an electron from a positively charged ion as compared to a neutral atom (Anthoni, 2006, 34).
Magnesium and Ionization Energy
Taking magnesium as an example in this case with an atomic number of 12. It lies in group II and group 3 with two valent electrons. The first IE is 737.7 KJ/mole while the second IE for the same element is 1450.7 KJ/mole.
Trends in Ionization Energy
The position occupied by an element in the periodic table determines the ionization of elements. Taking group two elements for example where magnesium belongs, ionization energy decreases down the group where beryllium has an ionization energy of 900 KJ/mole and strontium with ionization energy of 550 KJ/mole. The trends down the group are due to a successful increase in the number of energy levels which reduces the forces of attraction from the nucleus. The ionization energy for period three elements increases across the period due to increase in forces of attraction across the period (Earnshaw, 1997, 70).
References
Earnshaw, A., (1997). “Chemistry of the elements” (2nd Edn.), Oxford: Butterworth-Heinemann. ISBN 0-7506-3365-4.
Sharpe, A. G., (2008). “Inorganic chemistry” (3rd ed.). Prentice Hall. pp. 305–306. ISBN 978-0131755536.
Ash, R., (2005). “The top 10 of everything” 2006: the ultimate book of lists. Dk Pub. ISBN 0-7566-1321-3.
Anthoni, J.,(2006). "The chemical composition of seawater" ISBN 978-0131755536.
