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2×3=?
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The capital letters show the loud part of each word.
In the late 1940s and early 1950s, pilots from many countries needed one list everyone could say and hear. A language professor in Montreal, Jean-Paul Vinay, helped make it. Each word had to:
People from 31 countries tried the words out, and a word was kept if it was easy to understand next to the other code words. In 1956, five words that kept getting mixed up were swapped (Coca, Metro, Nectar, Union and Extra), and the G word went from Gold back to Golf. NATO countries led that last round of changes, which is why it is called the NATO alphabet.
Pilots say three as tree, which is easier for many speakers. Fower is stretched out so it isn’t mixed up with for. Fife can’t be mistaken for fire. Niner doesn’t sound like nein, the German word for no.
The official code words spell Alpha as Alfa and Juliet with two t’s. That way people who speak other languages say them the same way.
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Meet the elements, mix them into potions, and find out how atoms work.
Swipe the table sideways to see all 18 columns.
Dress up your element pals and spell words with elements.
Tap any element on the table to dress up a different pal. Each pal keeps its own outfit.
Tap a tile to meet that element on the table.
The small number under each symbol in the big tile is its standard atomic weight. Square brackets mean the element has no stable form, so the figure is the mass number of its longest-lived known version. “Ancient” means people were using it long before anyone kept records of discoveries.
Atoms join together to make everything around you. Pick the right ones and mix!
Tap ingredients to drop atoms into the cauldron, then mix!
What an element actually is, in six quick steps.
Your desk, the air, your cat and you are all made of atoms. They’re unbelievably small. Line up a million of them side by side and the row would be about as thick as a sheet of paper.
Atoms come in 118 known kinds, and they join together in endless combinations, the way 26 letters can spell every word in the dictionary.
A pure gold ring is made of gold atoms and nothing else, so gold is an element.
When different elements join up, you get a compound. Water is a compound: every water molecule is two hydrogen atoms stuck to one oxygen atom. That’s why its formula is H₂O.
Scientists know of 118 elements. 94 of them occur in nature, some only in tiny traces. The rest have only ever been made in labs.
In the middle is the nucleus, packed with protons and neutrons. Protons carry a positive (+) electric charge. Neutrons carry no charge at all.
Electrons are far smaller, almost 2,000 times lighter than a proton, and carry a negative (−) charge. They zip around the nucleus, held close because opposite charges attract.
Atoms are mostly empty space. If an atom were as big as a hockey arena, its nucleus would be about the size of a grain of sand at centre ice, yet it holds almost all of the atom’s weight.
The number of protons is an element’s atomic number, and it’s what makes each element itself. Every carbon atom has exactly 6. Add one more and it isn’t carbon any longer: it’s nitrogen.
In a normal atom the electrons match the protons, so the + and − charges cancel out. Neutrons add weight and help hold the nucleus together.
Electrons settle into layers called shells. The first shell holds just 2. For the first 20 elements, the next shells each fill up at 8 before a new one starts. Heavier atoms fill theirs in a trickier order.
The electrons in the outermost shell are the ones that meet other atoms, so they decide how an element behaves. Elements in the same column usually have the same number of outer electrons, which is why each column acts like a family.
Lithium, sodium and potassium each have one lonely outer electron they give away easily, which makes them very reactive. Neon’s outer shell is already full, so it doesn’t react at all.