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 ...

All of them were originally “missing” from a nearly completed row in the periodic table – the organized array of all the chemical elements in order of increasing atomic number. That’s the ...

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 ...