Elements and Atoms
Everything is made up of combinations of elements.
Element: An element is a pure substance. An element cannot be subdivided physically or chemically into anything other than itself. Elements are composed of atoms.
Atom: An atom is the basic building block of all matter. An atom is made up of a collection of basic particles that are arranged in a specific manner. The atom is the smallest unit of an element that has the characteristics of that element - no material can be broken in to smaller components than the atom and retain the properties of the material.
Nucleus: The center part of an atom composed of:
Neutron(s): neutral electrical charge; mass = 1.00894 amu*The nucleus is held together by strong nuclear forces and requires considerable energy to break apart. The result of breaking a nucleus apart is an atomic explosion (nuclear fission). The electrons are attracted to the protons in the nucleus by electrical forces and can be more easily removed.
Proton(s): positive (+) electrical charge; mass = 1.00 amu
The nucleus is surrounded by electrons.
Electron(s): negative (-) electrical charge; mass = 1/1837 amu*An amu (atomic mass unit) is the mass of a proton = 1.6597 X 10-24 grams.
The number of electrons and protons determine the atomic number. The balance between electrons and protons determines the charge of an ion; they are equal in a neutral atom.
The number of neutrons controls the atomic mass.
Bonds
Bonding is the way atoms obtain complete outer orbitals by adding electrons, giving up electrons, or sharing electrons to complete the outer orbital.
Addition or removal of electrons forms ions (charged atoms); positive ions are called cations; negative ions are called anions. The common types of bonding are:
Ionic: Give and take of electrons resulting in electrostatic attraction between ions. Na gives up an electron to form Na+. Cl accepts the electron to form Cl-. The result of this is NaCl (salt), an electrically balanced solid. (Why does it dissolve so easily in water?) Most minerals are made up of elements that are ionically bonded.
Covalent: Sharing of electrons between two electron clouds. In essence the shared electrons belong to both nuclei, and it is impossible to predict which cloud the electron will occupy at any given time.
Metallic: Sharing of an electron gas by metallic nuclei. Metals are highly conductive because the electrons are not tightly held by any one nucleus. The electrons belong to all nuclei in the material, and can easily move between nuclei.
Van der Waals: Weak electrostatic forces formed usually between different molecules that have dipolar moment due to shape of molecule.
Bonding leads to a structured arrangement of atoms in space. If the ordering is repetitive and predictable, the material will be crystalline. The arrangement of atoms in a molecule or a crystalline lattice is controlled the size of the respective atoms as well as the directionality (degree of covalence as well as which orbitals are involved) of the bonding.
Polymorphism - when two or more different minerals have the same chemical composition. E.g., diamond and graphite both have a chemical composition of C (carbon), but have have different crystal shapes - hence their very different properties.