The modern periodic table is arranged in ascending order according to atomic number. An element's atomic number is equal to the number of protons in each atom. Within this order, elements are arranged into distinct group... More »

In the modern periodic table, elements are arranged by atomic number. They are placed with the lowest atomic number first, and elements with increasing atomic numbers run to the right. They are also arranged in vertical ... More »

The modern periodic table is based upon the atomic number and the physical properties of each element. The periods, or rows, are arranged by increasing atomic number. Each column, or group, of elements has similar physic... More »

The modern periodic table is based upon the atomic number and the physical properties of each element. The periods, or rows, are arranged by increasing atomic number. Each column, or group, of elements has similar physic... More »

Henry Moseley's discovery of the atomic number refined the way elements are listed in the periodic table. Prior to his discovery, the elements were listed by atomic mass. Chemists considered the atomic numbers to be some... More »

"Rn" stands for radon in the periodic table. Radon's atomic number is 86, and its atomic weight is 222. Radon was originally called niton when it was discovered in 1900. More »

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In a color-coded periodic table of the elements, the box for each element is colored. This color represents the classes of elements, which include metals, metalloids and non-metals. In general, the color blue is used for... More »