We know that matter is made up of particles called atoms and that an element ... structure of sodium can also be shown in a diagram. Each dot represents an electron. Since the atomic number ...

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 ...

and led to a new form of chemistry in which isotopes have taken the place of elements, and fractional atomic weights have been superseded by integral atomic numbers. Atomic Structure and Spectral ...

Photo: Niels Bohr's research notes for his new atomic theory Rutherford's find ... emitted by the radioactive element radium) at a sheet of gold foil only 1/3000 of an inch thick, and tracing ...