In technology, matter is sometimes referred to as material substance.
It can be defined as anything known to exist and occupy space. Any
material substance consists of minute particles known as molecules;
these are the smallest particles of a substance which can exist and
maintain all the properties of the original substance. A molecule is
made up of a combination of two or more atoms of the elements. The atom
consists of various parts which are held together by forces, recognized
as being electrical in character. The forces of attraction come about
from unlike electrical charges. The constituent parts of an atom are the
central core or nucleus which has a positive charge and one or more
electrons. The electron has a negative charge. The nucleus is composed
of protons and neutrons (except the atom of hydrogen). Protons have
positive electrical charges and the neutrons are electrically neutral.
When an atom is electrically neutral it will have the same number of
protons and electrons. The number of electrons contained in an atom is
shown by the atomic number of the element. An atom becomes an ion when
the number of electrons is more or less than the number of protons. The
ion will be positive or negative according to the predominant electrical
charge. The atom of hydrogen is the simplest; it consists of one proton
and one electron. If the electron is removed from the atom of hydrogen
the remaining proton becomes a hydrogen ion which will be positive. In
some cases two atoms of the same element may differ in the number of
neutrons contained in the nucleus. The atomic weights will therefore be
different and the atoms are described as being isotopes of the element.
The isotopes of an element have identical chemical properties but
differing physical properties. The electrons outside the nucleus control
the properties of the atom, and the protons and neutrons in the nucleus
determine its atomic weight. The electrons are considered to form a
series of orbital envelopes or cases around the nucleus, each envelope
containing a set pattern of electrons. Other particles exist but need
not concern us in this study.