Biology Campbell Chapter 2

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Chapter 2 Terms
Matter - anything that takes up space and has mass.
Element - substance that cannot be broken down to other substances by chemical reactions. Compound - substance consisting of two or more different elements combined in a fixed ratio. Essential Element - the 20-25% of the 92 natural elements an organism needs to live a health life and reproduce. Trace Elements - required by an organism only minute quantities. Atom - the smallest unit of matter that still retains the properties of an element. Neutrons - electrically neutral

Protons - one unit of positive charge
Electrons - one unit of negative charge
Atomic Nucleus - the center of an atom
Dalton - the same as the atomic mass unit or amu.
Atomic Number - the number of protons, which is unique to that element Mass Number - the sum of protons plus neutron in the nucleus of an atom. Atomic Mass - the total mass of an atom.
Isotopes - different atomic forms of the same element.
Radioactive Isotope - one in which the nucleus decays spontaneously, giving off particles and energy. Energy - defined as the capacity to cause change for instance, by doing work. Potential Energy - the energy that matter possesses because of its location or structure. Electron Shells - each with a characteristic average distance and energy level. Valence Electrons - the electrons in the outermost electron shell. Valence Shell - the outermost electron shell.

Orbital - the three-dimensional space where an electron is found 90% of the time. Chemical Bonds - the interaction of sharing or transferring valence electrons, which result in staying close together. Covalent Bond - the sharing of a pair of valence electrons by two atoms. Molecule - two or more atoms held together by covalent bond. Single Bond - a pair of shared electrons

Double bond - two pairs of valence electrons are shared.
Valence - the bonding capacity of an element.
Electronegativity 0 the attraction of a particular atom for the...
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