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Levels of Biological Organization. The Chemical Context of Life. Chemical Elements and Compounds. Matter - anything that takes up space : has a mass and a volume. Example: DNA, ________ Is air matter? Yes OR No How can we prove this?.
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Chemical Elements and Compounds • Matter- anything that takes up space : has a mass and a volume. • Example: DNA, ________ • Is air matter? Yes OR No • How can we prove this?
Element- a substance that cannot be broken down into other substances • Example: sodium (Na) and chlorine (Cl) • Compound- a substance consisting of two or more elements. Example: Salt NaCl, HCO3 (important buffer involved in respiration)
Life requires approximately 25 chemical elements These six elements make 98% of all living organisms: - Carbon - Hydrogen - Nitrogen - Oxygen - Phosphorous -Sulfur (sulphur) (The remaining % = K, Ca, Na etc)
Trace Elements- small amount required by an organism, but very important. - example Iron or Iodine
Atom-smallest unit of matter made up of protons, electrons, and neutrons. Neutron: no charge Proton :+ charge Electron: -charge
Ion-Charged particle -cation: positive ion (Na1+) -Has one less electron, therefore it is positive -anion: negative ion (Cl1-) -Has one more electron, therefore it is negative
Atomic Number- Indicates the number of protons (can also predict size of the atom) He = 2 protons C = 6 protons (if the atom is neutral then the atomic # = the # of electrons) • Mass Number- sum of the protons plus the number of neutrons.
Standard Notation: 4 atomic mass # He element symbol 2 atomic # 12 C 6
Isotope- Different atomic forms of an element due to a different number of neutrons. Example: 12 13 14 C C C 6 6 6
Radioactive Isotopes are useful in -carbon dating -metabolism tracers -medicine
Why do some ions have less electrons? • Why do some ions have more electrons? • Think back to chemistry 11/Science 10/Science 9 • Outer Electron Shells/orbitals (valence electron shells) Bohr Models: First Shell: 2 electrons Second Shell: 8 electrons Third Shell: 8 electrons Fourth Shell: 18 electrons
Bohr Models • Lithium atom Chlorine atom
Bohr Models • Lithium Ion Chlorine Ion