Beyond the answers - interesting background to this quiz

The element that pulls electrons hardest

Fluorine tops the electronegativity scale, the measure of how strongly an atom attracts shared electrons in a chemical bond. That appetite explains why fluorine is such a reactive element and why it rarely appears alone in nature. It also shapes everyday life: fluorides in toothpaste help protect tooth enamel, and fluorine atoms turn up in many pharmaceuticals and non-stick coatings.

Three capitals, three very different stories

Tokyo is one of the world's largest metropolitan areas and has been Japan's political centre since the Tokugawa shogunate made Edo its seat of power. Dushanbe, Tajikistan's capital, takes its name from a Tajik word for Monday, a nod to the weekly market that once met there. Both cities show how a capital's name often carries its history rather than hiding it.

Following the Rhine from the Alps to the sea

The Rhine rises in the Swiss Alps and runs through or along several countries, including Switzerland, Germany, France and the Netherlands, before reaching the North Sea. For centuries it has been one of Europe's busiest waterways and a route for trade, travel and ideas. Its banks are lined with castles, vineyards and industrial cities that grew up around the river.

A capital on a river with a borrowed name

Austin, the capital of Texas, sits on the Colorado River - not the much larger Colorado that carved the Grand Canyon, but a Texan river of the same name. The city grew around the river's crossings and later dammed it to create a chain of lakes. Today the river runs through the heart of a city known for music, politics and technology.

The spider's eight-legged advantage

Spiders have eight legs, while parrots and horses have two and four respectively. That extra pair helps spiders move, sense vibrations and handle prey without relying on limbs built for walking alone. It is also a reminder that leg count is one of the quickest ways to tell major animal groups apart.