(5)īut why is it easier to remove these valence electrons as you go down group 2 from top to bottom. This strongly supports the concept that the electronic configuration of a Noble Gas (group 18) element is remarkably stable and that any atom or ion with this structure will not be chemically reactive.Īs a result, Group 2 elements form ionic compounds in which the group 2 cation has a charge of 2+. In general, it requires a bit less than twice as much energy to remove the second valence electron than it does to remove the first valence electron from a gaseous atom of each element.īut in general it requires more than double this amount of energy again in order to remove the third electron. So, let's look at the value of each third ionization for each group 2 element: Third ionisation: M 2+ (g) → M 3+ (g) + e. If we are right and the electronic configuration of a Noble gas (Group 18) element is particularly stable, then it should be very difficult, that is, require a lot more energy, to remove the third electron from each Group 2 element. You might also notice that the value of the second ionisation energy for each element is about double that of the first ionisation energy. That is, since it requires less energy to remove the two valence electrons as you go down the group, the chemical activity of these elements will increase going down the group. The suggestion here is that the chemical reactivity of the elements increase as you go down group 2 from top to bottom. So let's look at the values of the first and second ionisation energy for each Group 2 element (alkaline-earth metal):Īs you go down group 2 from top to bottom, the value of first ionisation energy decreases, it is progressively easier to remove the first valence electron.Īs you go down group 2 from top to bottom, the value of the second ionisation energy decreases, it is progressively easier to remove the second valence electron. If the value of the ionisation energy is low, then little energy is required to remove the electron, and the reaction is more likely to occur readily. If the value of the ionisation energy is high, then lots of energy is required to remove the electron, and the reaction is less likely to occur readily.
Second ionisation energy refers to the energy required to remove an electron (e -) from the gaseous ion with a charge of +1 (M + (g)) to form a gaseous ion with a charge of +2 (M 2+ (g)) as shown in the equation below: We can write a general equation to describe the removal of an electron (e -) from a gaseous atom (M (g)) to produce a gaseous cation with a charge of +1 (M + (g)) as: Ionisation energy (or ionization energy) is the energy required to remove an electron from a gaseous species.įirst ionisation energy (or first ionization energy) refers to the energy required to remove an electron from a gaseous atom. Trends in Ionisation Energy of Group 2 Elements
So, just how likely is it that a group 2 element will lose both valence electrons and form a cation. These patterns, or trends, recur throughout the periodic table and are referred to more generally as periodic trends, or, as periodicity.Īnd the cation of a group 2 element would therefore be chemically very stable (that is, no longer very reactive), just like a Noble Gas (group 18 element). The table below gives the name, atomic number, electronic configuration of the atom, the first, second and third ionisation energy, melting point, density and electronegativity, of the Group 2 elements (alkaline-earth metals).Ĭarefully inspect this data to find trends, or patterns, in the properties of group 2 elements.
Reactivity trend free#
No ads = no money for us = no free stuff for you! Table of Data for Group 2 Elements (e) Electronegativities decrease as successive energy levels (electron shells) are filled resulting in the positive nucleus exerting less of a force of attraction on electrons. Third ionization energy is much greater, about 4 times greater, than the second ionization energy for each element.
Second ionization energy is about double the first ionization energy for each element.