Chemical Basis of Life

784 WordsSep 14, 20054 Pages
Chapter 4 The Chemical Basis of Life Introduction • Your body is an elaborate chemical system. • Chemical signals between brain less enable your mind to understand what you see. • You nourish those cells with chemicals that are obtained from food. • Life is all about chemicals and how they interact Concept 4.1 Life requires about 25 chemical elements Elements • Humans and other organisms are examples of matter. Matter: Anything that occupies space and has mass. (Physical things) • The various forms of matter are composed of one or more chemical elements. Element: A pure substance that cannot be broken down into smaller substances by chemical means • There are 25 elements are essential to life. Four of these…show more content…
Isotope: An element with the same number of protons, but different number of neutrons. Radioactive Isotope: When the nucleus breaks down, or decays in an isotope, it gives off radiation in the form of matter and energy. This is then known as a radioactive isotope. • Radioactive isotopes have many uses in research and medicine. Living cells use radioactive isotopes just as they would use the non radioactive forms. They are then useful as "biological spies" for observing what happens to different atoms within organisms. • The particles and energy they give off can damage cells. • Most doses that are used in medical science however are safe. Electrons and Reactivity • The electrons determine how much an atom will react with others. • Elements differ in the amount of energy they have and how tightly they are held by the protons in the nucleus. Based on these properties chemists describe an atoms electrons as belonging to certain level of an atom that determines how that atom reacts. • The first level (nearest the nucleus) can hold 2 electrons while the second energy level can hold 8 electrons. • In the next section you will read more about the ways electrons are involved in the reaction among
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