BSC 114 Lecture Notes - Lecture 1: Mass Number, Valence Electron, Atomic Orbital
29 Aug 2016
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Document Summary
An organism is any contiguous living system (animals, plants, or bacterium) o o. Subject to basic laws of physics and chemistry. Living organisms are composed of matter- anything that takes up space and has mass. All biological matter is composed of elements- substances that cannot be broken down to other substances by chemical reactions. Compound is a substance consisting of two or more elements in a fixed ratio: has characteristics different from those of its elements. Of the 92 naturally occurring elements, anywhere from 20%-25% are essential to life: oxygen (o), carbon , and nitrogen (n) comprise roughly 96% of human body mass. Trace elements are those required by an orgnism in relatively minute quantities. An element"s chemical properties depend on the structure of its atoms- the smallest unit of matter that still retains the properties of an element o. Subatomic particles are what compose an atom. Protons have a positive charge o: neutrons have no electrical charge.
