Biology Exam1 chapter 2

Biology Exam1 chapter 2 - Chapter 2: Atoms and Molecules:...

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Chapter 2: Atoms and Molecules: The Chemical Basis of Life Pg. 26: Elements and Atoms Elements: substances that cannot be broken down into simpler substances Atom: smallest portion of an element that retains its chemical properties Matter: anything that takes up space and has mass Electron: particle that carries a unit of negative electric charge Proton: particle that carries a unit of negative electric charge Neutron: uncharged particle Atomic nucleus: protons and neutrons clustered together An atom is uniquely identified by its number of protons o Atomic number: number of protons in nucleus o Periodic table Protons plus neutrons determine atomic mass Isotopes of an element differ in number of neutrons Electrons move in orbitals corresponding to energy levels o Principal energy level electrons in orbitals with similar energies Pg. 29: Chemical Reactions If valence shell is not full, atom tends to lose, gain, or share electrons to achieve a full outer shell Atoms form compounds and molecules o Compounds: atoms of different elements combined o Chemical compound: atoms of two or more different elements combined in a fixed ratio o Molecule: two or more atoms joined very strongly Simplest, molecular, and structural chemical formulas give different information o Chemical formula: shorthand expression that describes the chemical composition of a substance o Simplest formula: empirical formula o Molecular formula: actual number (not necessarily reduced) o Structural formula: shows types, numbers of atoms and also arrangement One mole of any substance contains the same number of units o Molecular mass: sum of atomic masses of component atoms in single molecule o Avogadro’s number: 6.02 x 10
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This note was uploaded on 01/18/2012 for the course BIO 101 taught by Professor Martin during the Fall '08 term at Rutgers.

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Biology Exam1 chapter 2 - Chapter 2: Atoms and Molecules:...

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