earth science 2

earth science 2 - Prof. Jerry W. Kousen Vincennes...

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Prof. Jerry W. Kousen ERTH100 Vincennes University Intro to Earth Science Minerals The Earth is composed of rocks. Rocks are aggregates of minerals. Minerals are composed of atoms. In order to understand rocks, we must first have an understanding of minerals. In order to understand minerals we must have some basic understanding of atoms - what they are and how they interact with one another to form minerals. We'll start with the definition of a Mineral. Definition of a Mineral: Naturally formed it forms in nature on its own (some say without the aid of humans] Solid ( it cannot be a liquid or a gas) With a definite chemical composition (every time we see the same mineral it has the same chemical composition that can be expressed by a chemical formula). and a characteristic crystalline structure (atoms are arranged within the mineral in a specific ordered manner). Examples Glass - can be naturally formed (volcanic glass called obsidian), is a solid, its chemical composition, however, is not always the same, and it does not have a crystalline structure. Thus, glass is not a mineral. Ice - is naturally formed, is solid, does have a definite chemical composition that can be expressed by the formula H 2 O, and does have a definite crystalline structure when solid. Thus, ice is a mineral, but liquid water is not (since it is not solid). Halite (salt) - is naturally formed, is solid, does have a definite chemical composition that can be expressed by the formula NaCl, and does have a definite crystalline structure. Thus halite is a mineral. Atoms
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Atoms make up the chemical elements. Each chemical element has nearly identical atoms. An atom is composed of three different particles: Protons -- positively charged, reside in the center of the atom called the nucleus Electrons -- negatively charged, orbit in a cloud around nucleus Neutrons -- no charge, reside in the nucleus. Each element has the same number of protons and the same number of electrons. Number of protons = Number of electrons. Number of protons = atomic number . Number of protons + Number of neutrons = atomic weight . Isotopes are atoms of the same element with differing numbers of neutrons. i.e. the number of neutrons may vary within atoms of the same element. Some isotopes are unstable which results in radioactivity. Example: K (potassium) has 19 protons. Every atom of K has 19 protons. Atomic number of K = 19. Some atoms of K have 20 neutrons, others have 21, and others have 22. Thus atomic weight of K can be 39, 40, or 41. 40
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earth science 2 - Prof. Jerry W. Kousen Vincennes...

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