A Little About Atoms - 1
A LITTLE ABOUT ATOMS - 1
1. Introduction.
2. Types of Atoms.
3. Charged Atoms.
4. Plasma.
5. Nuclear Reactions - Fission.
6. Nuclear Reactions - Fusion.
INTRODUCTION
An element - one kind of atom
All matter is made of atoms. Atoms can be thought of a very small spheres measuring about one hundred millionth of a centimetre across. There are some 92 naturally occurring atoms though the exact number depends on who you talk to.
Some substances consist of only one kind of atom, a lump of iron consists of iron atoms. These materials are called elements.
Other substances consist of more than one kind of atom, water consists of one oxygen atom combined with two hydrogen atoms. These materials are called compounds. A number of atoms joined together to form one unit is called a molecule.
A compound - atoms join
Yet other substances are mixtures of elements and/or compounds, air is an example. These are called mixtures and they differ from compounds in that the atoms mix without combining as they do in a compound.
Although atoms are extremely small they are made up of smaller structures. In the centre of the atom is the nucleus only about a trillionth of a centimetre across. Electrons orbit around the nucleus.
A mixture - atoms don’t join
Electrons are unimaginably small specks of matter which carry a negative electric charge. All electrons have an identical electric charge and have the same mass.
A nucleus
The nucleus consists of protons and neutrons. Protons are about 2000 times heavier than an electron and carry a positive charge, opposite to that of an electron but of the same magnitude. Under normal conditions an atom will have the same number of electrons and protons so the number of positive charges will equal the number of negative charges and their effects will cancel out leaving the atom with no overall charge.
In all atoms except Hydrogen, the nucleus also contains neutrons. These are particles with slightly more mass than a proton but with no electric charge. The number of neutrons does not necessarily equal the number of protons. Because protons and neutrons have more mass than electrons most of the mass of the atom is concentrated in the nucleus.
Here are a few important constants.
Mass of electron 9.1093 X 10-28gram
Mass of proton 1.6726 X 10-24gram
Mass of neutron 1.6749 X 10-24gram
Charge of electron 1.6022 X 10-19coulomb