Magnesium

Magnesium is a chemical element – a substance that contains only one type of atom. Its official chemical symbol is Mg, and its atomic number is 12, which means that magnesium has 12 protons in it nucleus.

Magnesium compounds were first discovered in a region of Greece known as Magnesia. Some of the first uses were in the form of magnesium sulfate – better known by its common name Epsom salt . Legend says that a farmer in Epsom, England, wanted his cattle to drink water from a local well. The cattle did not like the bitter-tasting water, but the water was useful for healing skin conditions. People still use Epsom salt in their baths to ease sore muscles.

Magnesium

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On the periodic table of elements, magnesium is represented by the symbol Mg. It has an atomic number of 12 because it has 12 protons in its nucleus.

Magnesium granules image © Leiem/CC BY-SA 4.0

Rights: The University of Waikato Te Whare Wānanga o Waikato

Alkaline earth metals

Magnesium is grouped with the alkaline earth metals – sometimes referred to as group 2 elements – in the periodic table. The term ‘earth’ was used by early chemists. They initially recognised most of the group 2 earths in their oxide (or compound) forms before they were isolated as elements. They used the term earth to describe non-metallic substances that are stable when heated and not able to be dissolved in water. Alkaline means the oxides are basic or have a pH above 7.

The other elements in this group are beryllium, calcium, strontium, barium and radium. British chemist Humphry Davy used electricity to isolate magnesium and other group 2 elements in 1808.

Currently, we’ve discovered or created 118 elements. If scientists are able to create element 120, it will mostly likely belong to the alkaline earth metal group. Like radium, element 120 will also likely be radioactive.

Flash powder, fireworks and flares

Magnesium is an unusual metal in that it is difficult to ignite when there is a chunk of it, but when it is burning, it is very hard to extinguish. It continues to burn in nitrogen, carbon dioxide and even in water!

White fireworks

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Magnesium gives off a brilliant white light and is often used in fireworks.

Rights: NobbiP, CC BY-SA 3.0

On the other hand, magnesium powder and shavings are easy to ignite. When it burns, it gives off a brilliant white light. Magnesium powder was used as flash powder in the early days of photography. Now it is used in fireworks and marine flares. Outdoors enthusiasts often carry small blocks of magnesium – which they shave – to start their fires.

A very useful element

Magnesium is the fourth most common element in the Earth after iron, oxygen and silicon. There’s so much magnesium, we could create four very enormous objects – one the size of Mars and three the size of the Moon! It’s a good thing there is so much, because magnesium has so many uses.

Manufacturing

In its purest form, magnesium is comparable to aluminium. It is strong and lightweight, making it useful for manufacturing automotive components. It’s also used in mobile phones, laptop computers and other electrical devices. Magnesium alloys are becoming more common in the aerospace industry as the need for lightweight fuel-efficient aircraft grows.

Mag wheels

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Magnesium is an extremely light metallic structural material. In the 1950s and 1960s, racing wheels were developed from magnesium, hence the term ‘mag wheels’.

Pictured at the 2018 Geneva Motor Show is the 1968 Mustang fastback Steve McQueen drove in the movie Bullitt. It has American Racing Torq Thrust mag wheels.

Rights: Matti Blume, CC BY-SA 4.0

Biology – plants

Magnesium is vital for photosynthesis in plants. In fact, a magnesium atom forms the centre of every chlorophyll molecule. Plants use magnesium for other life processes too. Plants get their magnesium from the soil. It is often a macroelement in fertilisers.

Magnesium deficiency

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Plants require magnesium for photosynthesis. When there is not enough magnesium in the soil, plants will move magnesium (in chlorophyll molecules) from older leaves to younger leaves. The older, yellow leaves show symptoms of magnesium deficiency.

Rights: Public domain

Biology – animals

Like plants, animals require magnesium for their cells to function. Animals obtain magnesium from their local environment. Ruminants – cows and to a lesser extent sheep and goats – require magnesium supplements to reduce the risk of milk fever and grass staggers. Milk fever is most often linked with calving and birth – milk and colostrum production removes calcium from the blood. Magnesium helps the animals absorb calcium. Grass staggers occur when animals lack magnesium, often due to milk production and reduced magnesium content in spring pasture growth. Careful pasture and animal management is needed.

Biology - humans

Humans are also very dependent on magnesium. It is one of the seven macrominerals we require to stay healthy. Magnesium is needed for more than 300 biochemical reactions in our bodies. For example, ATP – the main source of energy in our cells – requires a magnesium ion in order to work. Magnesium is also central to maintaining our DNA and RNA structures.

The New Zealand Ministry of Health’s publication Nutrient Reference Values for Australia and New Zealand provides the recommended dietary intake for magnesium. (Note that pregnant and breastfeeding females may have different magnesium requirements.) Green vegetables, nuts and seeds are good sources of dietary magnesium.

Magnesium – recommended dietary intake (RDI) mg/day

Gender

Age group

RDI

Gender

Age group

RDI

Male

1–3 years

80 mg

Female

1–3 years

80 mg

Male

4–8 years

130 mg

Female

4–8 years

130 mg

Male

9–13 years

240 mg

Female

9–13 years

240 mg

Male

14–18 years

410 mg

Female

14–18 years

360 mg

Male

19–30 years

400 mg

Female

19–30 years

310 mg

Male

31+ years

420 mg

Female

31+ years

320 mg