CH 2 - Ch.2 - The Nature of Molecules Bio 1610 The...

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1 Ch.2 - The Nature of Molecules Bio 1610 • The bombardier beetle uses chemistry to defend itself 96% of the living matter is made of C, H, O, N Matter is any substance in the universe that has mass and occupies space All matter is composed of extremely small particles Atoms called atoms Every atom has the same basic structure Core nucleus of protons and neutrons Orbiting cloud of electrons Matter is made up of elements , substances that cannot be broken down to other substances by chemical reactions (e.g. Sodium) A compound is a substance consisting of two or more elements combined in a fixed ratio (e.g. Sodium chloride) Has characteristics different from those of its elements Sodium Chloride Sodium Chloride + A Helium Atom Electrons are kept in orbit by the attraction between the negatively charged electrons and positively charged protons Fig 2.5 Nucleus Atomic number: 2 (# of protons) Mass number: 4 (sum of the number of protons and neutrons in its nucleus Atomic Structure Neutral atoms have the same number of protons and electrons. Ions are charged atoms. cation have more 5 cation anion - cations – have more protons than electrons and are positively charged - anions – have more electrons than protons and are negatively charged Each element consists of a certain kind of atom that is different from those of other elements Atomic numbe An element’s properties depend on the structure of its atoms •Atomic number – Number of protons: e.g. carbon: 6 •Atomic mass (mass number) – Number of protons and neutrons: Carbon: 6 proton, 6 neutrons = 12
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2 the atomic number tells us the number of protons and the number of electrons that are found in a neutral atom of a specific element. Oxygen Oxygen Atomic number = 8 C 1 6 Atomic Number (# of Protons in an atom) The atomic number determines which element it is. 12 Mass number (atomic weight) ( # Protons + # Neutrons) Atomic Symbol (Carbon) # protons = atomic number # electrons = atomic number (in a neutral atom) # neutrons = mass number – atomic number Atoms with the same atomic number have the same chemical properties and belong to the same element . Electrons are located 9 in orbitals. Atoms with the same number of protons and electrons are neutral Atoms in which the number of electrons does not equal the number of protons are called ions (charged particles). An atom with more protons than electrons has a net positive charge (cation) An atom with fewer protons than electrons has a negative charge (anion). 99% of all carbon Different • Isotopes are atoms with the same number of protons but different numbers of neutrons Atomic Weight (mass number) may Vary ~1% Minute quantities atomic mass Same atomic number Stable isotopes Radioactive: the nucleus decays Radioactive isotope dating Use to date fossils less than 50,000 years old. Fossils older than 50,000 years
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This note was uploaded on 09/28/2010 for the course BIO 1620 taught by Professor Bybee during the Fall '06 term at Utah Valley University.

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CH 2 - Ch.2 - The Nature of Molecules Bio 1610 The...

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