BIO SCI 93 Chapter Notes - Chapter 2: Electron Shell, Iodine Deficiency, Covalent Bond
23 Oct 2018
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BIO SCI 93 Full Course Notes
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Humans need 25 elements, plants need 17. Four elements: oxygen, carbon, hydrogen, and nitrogen makes 96% of living matter. Calcium, phosphorus, potassium, and sulfur makes up 4% Trace element: required by organisms in only minute quantities. Iron is needed by all forms of life. Iodine deficiency: diet that causes the thyroid glands to grow to abnormal size, a condition called goiter. First shell is closest with lowest potential energy, second containing higher potential energy. Electrons can move shell to another, by only gaining or losing amount of energy equal to the difference in potential energy. Dependent on number of atomic number (electrons) Hydrogen -> helium is in first shell. Lithium -> neon is in second shell. Sodium -> argon is in third shell. Elements with complete valence shell is unreactive. Unreactive: not interact readily with other atoms. Other elements that are not complete are called inert. Electrons are found 90% of the time in three dimensional space.
