Guess the Element

A new element to work out every day. You get six guesses, and after each one the game tells you how close you were on atomic number, group, period, and the kind of element it is. Everyone gets the same element on the same day.

How to play

Type any element name or symbol and press Guess. The game will not accept something that is not a real element, and it will not let you waste a guess by repeating one. You have six tries.

Each guess comes back with five clues, read left to right:

• ✓ Green means that clue is an exact match with the answer.
• ~ Amber means you are close: within 10 on atomic number, within 2 on group, or one row away on period.
• ✕ Grey means no match.
• ↑ An arrow on the number, group, or period tells you which way to move. Up means the answer is higher than your guess.

What the five clues mean

Number is the atomic number, the count of protons in the nucleus. It is what makes an element that element, and it is the number the periodic table is ordered by.

Group is the column, numbered 1 to 18. Elements in the same group have the same number of outer valence electrons, which is why they behave alike. Group 1 is the reactive alkali metals; group 18 is the unreactive noble gases.

Period is the row, numbered 1 to 7. It tells you how many electron shells the atom has. Going down a period number adds a shell, which is why atoms get bigger down the table.

Category is the family the element belongs to: alkali metal, alkaline earth metal, transition metal, post-transition metal, metalloid, reactive nonmetal, halogen, noble gas, lanthanide, or actinide.

Metal? is the broadest split of all: metal, metalloid, or nonmetal. Getting this one green early cuts the table roughly in half.

Two rules worth knowing

The answer is always one of the first 86 elements, hydrogen through radon. Those are the ones that turn up in a chemistry course and that you can actually get hold of. You can still guess any of the 118 if you want to test a hunch about a heavier one.

The lanthanides and actinides sit in their own two rows underneath the main table and do not really have a column of their own. This game counts them as group 3, which is where they slot into the full-width version of the table.

A strategy that works

Open in the middle rather than with your favorite element. A first guess somewhere around atomic number 40 to 50 splits the range in half whichever way the arrow points, and it will usually land you on a transition metal, which settles the metal question straight away.

After that, chase the clue that removes the most elements. Period is usually worth more than atomic number early on, because pinning the row down to one of seven leaves you a single line of the table to search. Once you know the row and the column, there is only one element that can sit there.

Category is the clue people waste. If it comes back green on "halogen", you are down to five candidates before you have used a second guess. If it comes back grey, you have still ruled out a whole family.

Why this is worth doing

Reading the periodic table and using it are different skills. Most students can find an element when they are told its name, but freeze when they have to work backwards from properties. That is the skill this game drills, and it is the one exams actually test.

The layout is not arbitrary. Mendeleev arranged it so that elements with similar behavior line up, and he left gaps where he thought undiscovered elements belonged. He was right. Every time you narrow a guess by reasoning "it is in group 17, so it is a halogen, so it is reactive and forms salts", you are using the same logic he built the table on.

If you want to look at the whole table while you play, open the interactive periodic table in another tab. It is not cheating. Chemists keep one on the wall.

Frequently asked questions