KnowSoda
ScienceChemistry
Atoms & the Periodic Table: fun facts and quiz
The essentials in 7 ideas, with fun facts, an illustrated story and a quiz to see how much you know.
The essentials
Atoms
Everything is made of atoms: a tiny nucleus of protons and neutrons, with electrons around it. Atoms are almost entirely empty space.
Key fact
A full stop on a page is millions of atoms wide.
Chemical Elements
An element is a substance made of one kind of atom, set by its number of protons. Hydrogen has one, carbon six, and gold 79.
Key fact
118 elements are known so far.
The Periodic Table
The periodic table lists the elements in order of their proton count. Dmitri Mendeleev built an early version in 1869, leaving gaps for elements not yet found.
Key fact
Elements in the same column behave in similar ways.
Everyday Elements
Your body is mostly oxygen, carbon, hydrogen and nitrogen. Earth’s crust is mostly oxygen and silicon, and the air is mostly nitrogen.
Key fact
Air is about 78% nitrogen and 21% oxygen.
Molecules & Bonds
Atoms join into molecules by sharing or swapping electrons. Water is two hydrogen atoms bonded to one oxygen atom: H₂O.
Key fact
Table salt, NaCl, is sodium and chlorine joined together.
Metals
Most elements are metals: shiny, and good at conducting heat and electricity. Mercury is the only metal that’s liquid at room temperature.
Key fact
Gold can be beaten into sheets thinner than a hair.
Noble Gases
Helium, neon and argon are noble gases. Their atoms rarely react with anything, which makes them useful in balloons, signs and light bulbs.
Key fact
Neon glows red-orange; other sign colours use other gases.
Fun facts
If an atom were the size of a football stadium, its nucleus would be about the size of a pea in the middle.
Hydrogen, the simplest element, makes up about three quarters of all the ordinary matter in the universe.
Mendeleev predicted the elements gallium and germanium before anyone had discovered them.
An adult body holds about 4 grams of iron, roughly enough to make one small nail.
A single glass of water holds more molecules than there are stars in the observable universe.
Gallium is a metal that melts in your hand: its melting point is about 30 °C.
Helium is named after Helios, the Greek god of the Sun.
Story: The Shell That Bounced Back
The Shell That Bounced Back
1909, Manchester. Ernest Rutherford’s team fires tiny particles at gold foil thinner than a page, expecting them to fly straight through.
Most do. But a few bounce right back, which Rutherford said was like firing a shell at tissue paper and having it hit you.
The atom’s mass had to sit in a tiny, dense centre: the nucleus. They had found the heart of the atom.
True or false?
Tap your answer to see if you got it, and why.
-
Question 1 of 10
Atoms are mostly empty space.
Show the answer
True. The nucleus is tiny compared with the whole atom.
-
Question 2 of 10
Atoms with the same number of protons are the same element.
Show the answer
True. The proton count is what defines an element.
-
Question 3 of 10
Mendeleev created an early periodic table in 1869.
Show the answer
True. And left gaps for undiscovered elements.
-
Question 4 of 10
Oxygen makes up about a fifth of the air.
Show the answer
True. About 21%.
-
Question 5 of 10
A water molecule has two hydrogen atoms and one oxygen atom.
Show the answer
True. That’s what H₂O means.
-
Question 6 of 10
Mercury is liquid at room temperature.
Show the answer
True. The only metal that’s liquid at room temperature.
-
Question 7 of 10
Noble gases rarely react with other elements.
Show the answer
True. Their outer electron shells are already full.
-
Question 8 of 10
Electrons sit inside the nucleus.
Show the answer
False. The nucleus holds protons and neutrons; electrons are around it.
-
Question 9 of 10
Changing the number of neutrons turns an atom into a new element.
Show the answer
False. It makes a different isotope of the same element.
-
Question 10 of 10
The periodic table lists elements in alphabetical order.
Show the answer
False. They’re in order of proton count.
Keep going in the app
KnowSoda learns what you know and brings back what you’re about to forget. Atoms & the Periodic Table has 6 more ideas at the Advanced and Expert levels.
