chapter 2 review

chapter 2 review - Lecture 3 Chapter 2 Atoms Molecules The...

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Lecture 3: Chapter 2 – Atoms & Molecules: The Chemical Basis of Life I. Elements & Atoms A. Important Elements Carbon, Hydrogen, Oxygen, & Nitrogen are the most abundant elements in living things (about 96% of mass) 1. Carbon backbone of organic molecules 2. Hydrogen component of water 3. Nitrogen component of proteins, nucleic acids, & chlorophyll 4. Oxygen required for cellular respiration component of water B. Atom 1. Nucleus contains protons (+) & neutrons (uncharged) 2. Electrons () surround nucleus Each atom is a particular element identified by the number of protons (atomic number) C. Atomic Mass sum of protons & neutrons D. Atomic Mass Unit Mass of a single proton or neutron Mass of an electron about 1/1800 of an A.M.U. Atomic mass typically written as a superscript & atomic number written as subscript; ex. 16 8 O E. Isotope – alternate form of an element with the same number of protons & electrons, but a different number of neutrons and therefore a different mass
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Unstable isotope goes through process of decay to stable isotope, by emitting radiation ( ϐ particles) F. Orbitals Electrons move rapidly in electron orbitals outside the nucleus 1. Electron shell – electrons in orbitals with similar energies, said to be at the same principal energy level 2. Valence electrons most energetic electrons, which occupy the valence shell represented as the outermost concentric ring in a Bohr model An atom tends to lose, gain, or share electrons to fill its valence shell, when not full II. Chemical Reactions A. Molecules A molecule consists of atoms joined by covalent bonds The molecular mass of a compound is the sum of atomic masses of its component atoms for each single molecule The
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