Atomic Structure

atomic structurenoun Physics . the structure of an atom, theoretically consisting of a positively charged nucleus surrounded and neutralized by negatively charged electrons revolving in orbits at varying distances from the nucleus, the constitution of the nucleus and the arrangement of the electrons differing with various chemical elements.

In the last lesson we learned that atoms were particles of elements, substances that could not be broken down further.  In examining atomic structure though, we have to clarify this statement.  An atom cannot be broken down further without changing the chemical nature of the substance. Atoms are made up of 3 types of particles electrons , protons and neutrons .  These particles have different properties.  Electrons are tiny, very light particles that have a negative electrical charge (-). Protons are much larger and heavier than electrons and have the opposite charge, protons have a positive charge.  Neutrons are large and heavy like protons, however neutrons have no electrical charge.  Each atom is made up of a combination of these particles.  Let's look at one type of atom:

 John Dalton was the first scientist to compose a theory of matter based 

on atoms. Dalton's atomic theory ins based on four concepts. He stated: 

     "1. All elements are composed of ato

ms, which are indivisable and 

indestructable particles. 

     2. All atoms of the same element are exactly alike; in particular, they 

have the same mass. 

     3. Atoms of different elements are different; in particular, they have 

different masses. 

     4. Compounds are formed by the joining of atoms of two or more 

elements." 1 

Dalton's Atomic Theory |

Democritus first suggested the existence of the atom but it took almost two millennia before the atom was placed on a solid foothold as a fundamental chemical object by John Dalton (1766-1844). Although two centuries old, Dalton's atomic theory remains valid in modern chemical...