This year marks the 150th anniversary of the publication of Mendeleev’s Periodic Table of Chemical Elements in 1869. In celebration, the United Nations Educational, Scientific, and Cultural ...

See if you can organize the first 25 elements of the periodic table in order in the quiz below. The periodic table as we know ...

The finished puzzle is a section of the periodic table, so the numbers on each tile are their atomic numbers - that means they increase from left to right and top to bottom. Another helpful clue ...

The periodic table was arranged by atomic mass, and this nearly always gives the same order as the atomic number. However, there were some exceptions (like iodine and tellurium, see above), which didn ...

They can have different labels on the groups or numbers in the rectangles. However, the elements never move places. The periodic table's layout means we can make predictions about elements based ...

If it has 7 protons, that’s nitrogen. But the logic of the periodic table also relies upon the number and organisation of electrons in an atom. Let’s take chlorine as an example. It is ...

often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic number. Scientists use the periodic ...