Chapter 2 notes

Chapter 2 notes - Chemical basis in life (chapters two and...

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Chemical basis in life (chapters two and three) Living things obey the same laws as non-living things do. Element - the substance that cannot be broken down by chemical means - 92 occur in nature if if if if she as - 25 are found in living things - In a human being 96% of total body weight is made up of the elements carbon hydrogen and oxygen and nitrogen - The other 4% are made up of P and 20 others (many are present in trace amounts, which is less than 0.01%) Atom - smallest unit of an element Atoms are composed of: Nucleus - Protons - one unit of positive charge and equal to 1 AMU - Neutrons - no charge and equal to 1 AMU Electrons - Electrons for a cloud around the nucleus - One unit negative charge - 0.0005 AMU (negligible) An atom is electrically neutral, whereas the number of electrons is equal to the number of protons The atomic number is equal to the number of protons The mass number is equal to the number of protons and neutrons and the nucleus Shorthand descriptions of the atoms: 12 C superscript equals mass number 6 C subscript equals atomic number
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- Atoms of the same element always have the same number of protons, but they could have a different number of neutrons. Isotopes - Atoms of the same element that have a different number of neutrons Radioactive isotopes - unstable nucleus - They decay releasing energy and particles which can be detected
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Chapter 2 notes - Chemical basis in life (chapters two and...

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