Bio1_05_Chemistry - 1 2 3 4 1 2 5 6 7 1 2 8 1 2 Overview Ch 2 Basic Chemistry Chemical elements Compounds molecules Water Acids bases Chemical Elements

1 Overview • Ch. 2: Basic Chemistry – Chemical elements – Compounds & molecules – Water – Acids & bases Chemical Elements • Elements – Substance that cannot be broken down into simpler substances • Atoms – Smallest part of an element with properties of that element Elements in Cells • 96% : H, C, N, O • Remaining 4%: Ca, P, K, S, Na, Cl, Mg, Fe, I, Cu, Mn, Co, Zn, + trace Atoms • Atom – Proton ( p + ) – Neutron ( n 0 ) – Electron ( e - ) in electron shell • Mass number – # protons + # neutrons • Atomic number – # protons Example: Carbon Periodic Table • Appendix D of text – Partial: Figure 2.3 • Atomic mass – Average AMU for all isotopes • Atoms in same group – Similar binding characteristics – Group VIII: noble gases Isotopes • Differ in # neutrons • Radioactive isotopes* • Low levels of radiation – Tracers – Image body’s organs and tissues • High levels of radiation – Irradiation to kill pathogens – Radiation therapy to kill cancer cells Electrons & Energy • Electrons – Not possible to determine exact location • Electron shells = energy levels – The Bohr model – 1 st level: 2 e - – 2 nd & 3 rd levels: 8 e - – Valence shell = outer shell • Octet rule – Outer shell most stable when full 1 2 3 4 1 2 5 6 7 1 2 8 1 2