This graphic looks at the colours of transition metal ions when they are in aqueous solution (in water), and also looks at the reason why we see coloured compounds and complexes for transition metals. This helps explain, for example, why rust (iron oxide) is an orange colour, and why the Statue of Liberty, made of copper, is no longer the shiny, metallic orange of copper, but a pale green colour given by the compound copper carbonate.
This graphic looks at the colour of various metal and metalloid ions that occur during flame tests. Most people probably remember doing this experiment in school chemistry lessons, if not with the full range of ions shown here, but, for the uninitiated, a brief explanation of the origin of the colours follows.
The colours in fireworks stem from a wide variety of metal compounds – particularly metal salts. ‘Salt’ as a word conjures up images of the normal table salt you probably use every day; whilst this is one type of salt (sodium chloride), in chemistry ‘salt’ refers to any compound that contains metal and non-metal atoms ionically bonded together. So, how do these compounds give a huge range of colours, and what else is needed to produce fireworks?
I’m making pH indicator paper with some of my classes this week, using the coloured leaves of red poinsettia plants, which set me thinking about the chemistry behind why these plants can be used as indicators.
Poinsettias have a reputation for being poisonous – a claim that is in fact entirely unfounded. A quick google search will reveal that the myth of poisonous poinsettias potentially originates from a ingestion of poinsettia leaves being mistakenly attributed as the cause of poisoning of an american child in 1919. Not being poisonous obviously isn’t quite the same as being edible, and eating poinsettia leaves can potentially cause stomach pain and vomiting – but there have been no recorded deaths as a result of the plant. As its leaves also have a reportedly ‘indescribably awful’ taste, few could probably bear more than a nibble.
