Introduction to Physical Science/Atoms< Introduction to Physical Science
Atoms are the smallest pieces of matter that still retain elemental form. An atom is rarely alone in space, but is more likely to be grouped with other atoms to form molecules. Molecules are groups of atoms that form either pure elements (all of one type of atom) or compounds (mixtures of different types of atoms within a molecule) Atoms are usually depicted as a transparant globe containing a nucleus and its attendant electrons. The transparant globe is the Atomic Wall.
Atoms contain several component particles.
- Proton -- a nucleaic particle with Atomic Weight of 1au containing a positive charge
- Neutron -- a nucleaic particle with Atomic Weight of 1au containing a neutral charge
- Electron -- a nucleaic particle with Atomic Weight of 0.0009au containing a negative charge
While protons and neutrons are always grouped together in the center at the nucleus, electrons orbit in electron shells within the electron cloud
It contains protons (particles with a mass of one Atomic Unit containing a positive charge) and neutrons (particals with a mass of one atomic unit and a neutral charge). The nucleus is the most massive piece of the atom, containing 99.99% of the atom's mass. The second part of the atom is the electron cloud which is made up of several electron shells.
The picture to the right is of a Helium-2 atom. It contains 2 protons (red circles), 2 neutrons (green circles), and 2 Electrons (yellow circles). In an atom, the number of protons must be equal to the number of neutrons or the atom would collapse.
This atom is regular helium or Helium-2. Helium-2 is the first, most stable isotope of helium. Isotope is noted in an atomin name by the number following the Element which is always equal to the number of neutrons in a single atom of that isotope. Neutrons are the only particles that can be added or removed within an atom without changing the elemental properties. However, changing the isotope of a substance can alter more minor features. Changing the isotope of Uranium cannot make it a gas, but it can, for example make the Uranium more radioactive. When a particle is given more neutrons than the nuclear force can hold within the atom they begin to be released. Depending on the element, this process can take any amount of time from a few miliseconds to millions of years. This time of loss of neutrons is called a half-life and the process of losing particles is called decay. Isotopes that have this decay are known as Unstable Isotopes Unstable Isotopes usually decay untill they reach a point where they become stable again. However, some elements have no stable isotopes, and therefore will continue to decay, losing protons and electrons in the process creating a lighter, more stable element altogether.