Map of Singapore found in the Atlas Miscelâna of 1615 (redrawn by Peter Borschberg in 2017)

1. Tanah Merah means red land in Malay

Singapore in the 15th century was very different. It was mainly visited by the Portuguese, spelled as Sincapura in their language, and drawn in a funny shape on their map. But one thing was the same – Tanah Merah already existed as a place.

Tanah means land; and merah, red. The indigeneous orang laut named it after the colour of the soil there, which is a mixture rich in iron(III) oxide.

Transition elements are highlighted orange

2. Iron(III) oxide contains the transition element iron

Iron(III) oxide is an ionic compound. Its cation is iron(III), which is a transition element occupying the block between Group II and Group III in the Periodic Table.

The roman numeral within the brackets tell us the charge of the cation in the compound. So iron(III) has a charge of 3+ and we can write its formula as Fe3+.

Laterite soil rich in iron(III) oxide at a quarry in India, similar to the soil at Tanah Merah

3. Iron(III) dyes the soil merah

As a transition element, the iron(III) cation gives iron(III) oxide its characteristic red colour.

And since the soil at Tanah Merah has a high composition of iron(III) oxide, it appears red to us. We call this type of soil laterite, which is common in wet and rainy tropical countries. The frequent rain washes away the more soluble components of soil, leaving behind the insoluble minerals like iron(III) oxide.

In the ancient city of Angkor in Cambodia, engineers and workmen used laterite to line canals and spillways a thousand years ago.

Most compounds containing transition element are coloured.

Dark green iron(II) hydroxide precipitate in light green iron(II) nitrate solution

4. But iron(II) is green with envy

Not all compounds of iron are red.

Like most transition elements, iron can form ions of variable oxidation state. Simply put, iron can lose different number of electrons to form either iron(II) with a charge of 2+ or iron(III) with a charge of 3+.

While iron(III) ions tend to form red compounds, iron(II) ions give rise to green compounds. For example, iron(II) nitrate and iron(II) hydroxide are both green.

Most transition elements have variable oxidation state.

5. Transition elements are hardcore metals

While iron(III) oxide is red, we can react it with carbon to extract pure iron that looks silvery-grey.

Transition elements on their own are metals with a giant metallic structure that conducts electricity. That’s why we often call them transition metals.

However, transition metals have hardier physical properties than metals from Group I, II and III. Their melting point and density are much higher.

For example, while potassium from Group I has a really low melting point of 64 °C, iron has a dramatically higher melting point of 1538 °C.

Of course, like any other topic in chemistry, there are exceptions. While mercury is a transition element, its melting point of -39 °C is so low that it exists as a liquid at room temperature.

Most transition metals have a higher melting point and density than main group metals.

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