Chapter 2 - CHAPTER 2 THE CHEMICAL CONTEXT OF LIFE I. II....

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THE CHEMICAL CONTEXT OF LIFE I. All life is characterized by chemical reactions. II. Somewhere in the transition from molecules to cells we also transition from non-life to life. III. Matter – Anything that takes up space and has mass. A. Element – a substance that cannot be broken down into other substances by chemical reaction. B. There are 92 different elements identified to date. C. Elements are represented by symbols, i.e. hydrogen is H and oxygen is O. D. 25 of the 92 are essential to life. C, O, H & N make up 96% of living matter. P, S Ca and K compose almost all of the remaining 4%. Essential trace elements include Fe, I, Zn, etc. IV. Properties of Elements A. Atom – smallest unit of matter that retains the properties of an element. B. Subatomic particles 1. Subatomic nucleus – composed of protons and neutrons. 2. Electrons – form a cloud of movement around the nucleus. 3. Protons carry a + charge. Electrons a – charge. Neutrons carry no charge hence are electrically neutral. 4. Dalton – a unit of measure equal to the weight of the atomic mass unit or amu. Protons and neutrons are about 1 dalton each. 5. All elements are characterized by the number of protons they contain. This number is called the atomic number and is found as a subscript to the left of the element’s symbol. 6. Mass number – the number of protons and neutrons. This number is found as a superscript to the left of the element’s symbol. 7. Atomic mass – total mass of an atom, or the total of
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Chapter 2 - CHAPTER 2 THE CHEMICAL CONTEXT OF LIFE I. II....

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