The second column elements of the periodic table are known as the alkali earth metals. They are like group 1 in that they are relatively soft metals that react with water to produce hydrogen gas however they don’t react as vigorously.
This is due to the group 2 elements having 2 outer electrons instead of one. This is a slightly more energetically favourable electron configuration, meaning the atoms in group 2 are happier with two electrons whizzing around the nucleus than group 1 metals are with their single electron, who just want to give it away as quickly as possible to form their preferred state as a positive metal ion (M+, where M stands for a metal).
Group 2 metals aren’t precious about their two electrons though. They are also happy to exist as positive metal ions that have lost their negatively charged electrons, but they tend to form M2+. If they formed M+ they would then have a similar electron configuration to a group 1 element which we know isn’t very stable and would get rid of that second electron as quickly as they can.
This relatively lower reactivity means that group 2 elements are often used in portable hydrogen generators because they release hydrogen slowly enough that there isn’t sufficient heat energy given out over the course of the reaction to ignite the flammable hydrogen gas – which is what we see when group 1 metals react with water.
Group two metals are shiny and usually silvery-white in colour. Some occur naturally as free elements but are often found as ores (typically metal oxides) in the ground and the metal needs to be extracted from those compound mixtures.
Much like Group 1 the reactivity of the metals increases going down the group because the outer electrons become further away from the nucleus with the increasing number of electrons moving around the nucleus, making them easier to remove – much like how a paperclip becomes easier to manipulate the further away it is from a magnet.
The metals react with water to form metal oxides but because of their 2-electron valency, they form hydroxides with the general formula M(OH)2 as hydroxide (OH–) ions have a single negative charge so two are needed to balance the double positive metal ion (M2+). Beryllium is the exception which has a sufficiently protective oxide layer.
They also react with oxygen to form metal oxides and with halogens, such as chlorine, fluorine etc., to form metal halides.
Throughout group 2 we’ve learned about beryllium’s niche role in missiles and rocket parts; the bright light burning magnesium produces which is used in old photography flashes, flares and fireworks; calcium’s key role in forming our bones and teeth and how strontium can be used to mimic calcium to treat osteoporosis; and the lesser used barium and radium which are used for treating digestive disorders and prostate cancer respectively.
I hope you’ve enjoyed our tour of group 2. Now we move on to the central block of the periodic table, known as the transition elements which spans groups 3 to 10! Keep an eye on the Instagram account for individual posts about each element as well as other content about my life in the chemistry lab.
What’s your favourite element? How are you marking #IYPT2019 ? Let me know in the comments below.