ATOM

Atoms are the smallest subdivision of matter that can still be recognized as a particular element. Atoms themselves can be broken down into smaller, subatomic particles. There are three subatomic particles of interest:

1. Electrons: 1- electric charge and 9.1 x 10-28 grams
2. Protons: 1+ electric charge and 1.7x 10 –24 grams
3. Neutrons: carry no electric charge and weigh slightly more that a proton.


In the Bohr model, the atom is conceived as having most of its mass in an extremely small central region called the nucleus. The protons and neutrons are in the nucleus. The electrons are confined to orbits at prescribed distances from the nucleus. These orbits are known as levels or shells. Each shell has a letter designation: The innermost shell called the K-shell may contain one or two electrons. The next shell is known as the L- shell; it is further from the nucleus and may contain up to eight electrons. The remaining shells for the electrons ar...