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

The electrons surround the nucleus in 3 dimensions but it is easier to show an energy level model in two dimensions ... The atom with eight protons in its nucleus (atomic number 8) is oxygen. Each ...

Substances have both physical and chemical properties. Developing the periodic table The periodic table was developed by grouping elements with similar properties. This, together with a later ...