Chapter2 Lecture Notes Fall07

Chapter2 Lecture Notes Fall07 - Most Common Elements in...

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1 Most Common Elements in Living Organisms Oxygen Hydrogen Carbon Nitrogen Fig. 2-1, p.16 human body Oxygen 61.0% Carbon 23.0 Hydrogen 10.0 Nitrogen 2.6 Calcium 1.4 Phosphorus 1.1 Potassium 0.2 Sulfur 0.2 earth’s crust Oxygen 46.0% Carbon 27.0 Hydrogen 8.2 Nitrogen 6.3 Calcium 5.0 Phosphorus 2.9 Potassium 2.3 Sulfur 1.5 What Are Atoms? Smallest particles that retain properties of an element Made up of subatomic particles: – Protons (+) – Electrons (-) – Neutrons (no charge) Isotopes Atoms of an element with different numbers of neutrons Behave the same way in chemical reactions Radioisotopes emit particles and energy as they decay, eventually becoming a different element
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2 What Determines Whether Atoms Will Interact? The number and arrangement of their electrons Electrons Carry a negative charge(-) Repel one another Are attracted to protons in the nucleus Move in orbitals (volumes of space that surround the nucleus) Electron Orbitals Orbitals can hold up to two electrons Atoms differ in the number of electrons in orbitals Orbitals closest to nucleus are lower energy and are filled first First shell Lowest orbital, holds 2 electrons Second shell 4 orbitals hold up to a total of 8 electrons Unfilled shells make atoms likely to react Fig. 2-2, p.17 hydrogen 1p + , 1e helium 2p + , 2e carbon 6p + , 6e oxygen 8p + , 8e sodium 11p + , 11e chlorine 17p + , 17e neon 10p + , 10e electron proton neutron The Shell Model
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3 Chemical Bonds, Molecules,
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This note was uploaded on 01/05/2009 for the course BIO 111 taught by Professor Goschke during the Spring '07 term at Cal Poly.

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Chapter2 Lecture Notes Fall07 - Most Common Elements in...

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