AP Bio Quiz Study Guide 10_6_19 - Chemical Context of Life \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf \u25cf Organisms

AP Bio Quiz Study Guide 10_6_19 - Chemical Context of...

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Chemical Context of Life Organisms are composed of matter ● Matter : takes up space and has mass ● Matter : made up of elements ● Element : any substance that cannot be broken down by chemical reactions Has unique atoms ● Compound : a substance consisting of two or more elements in a fixed ratio A compound has different characteristics than its elements 25/92 elements essential to life 96% of living matter--carbon, hydrogen, oxygen, nitrogen 4%--calcium, phosphorous, potassium, sulfur Trace elements : required by organisms in small quantities ● Atom : the smallest unit of life that retains the property of an element Subatomic particles : atoms are composed of Electrons--negatively charged Form a cloud around the nucleus Protons--positively charged Neutrons--no charge Atomic number : number of protons in its nucleus Mass number : the sum of protons and neutrons in the nucleus Atomic mass : total mass (approximated by mass number and avg of isotopes) ● Isotopes : two atoms of an element that differ in the number of neutrons All atoms of an element have the same number of protons Radioactive isotopes decay spontaneously and give off energy Dating fossils Tracing atoms through metabolic processes Diagnosing medical disorders ● Energy : the capacity to cause change Potential energy is the capacity to cause change ○ Electron ’s state of potential energy is its energy level (electron shell) 1st shell--lowest energy level 2nd shell--higher energy level 3rd shell--highest energy level Valence electrons : electrons in the outermost shell (valence shell)
Noble gasses have a full valence shell and are inert Chemical behavior determined by valence electrons ● Orbital : the area where electrons are found Each shell has a specific amount Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms These interactions usually result in atoms staying close together, held by attractions called chemical bonds Covalent bond: the sharing of a pair of valence electrons by two atoms The shared electrons count as part of each atom’s valence shell ● Molecule : single bond or double bond Structural formula : represents atoms and bonding (H-H) Molecular formula : (empirical) further abbreviation (H2) ● Valence : bonding capacity ● Compound : the combination of two or more different elements ● Electronegativity : atom’s attraction for electrons in a covalent bond Nonpolar covalent bond : atoms share electrons equally Polar covalent bond : one atom is more electronegative and sharing of electrons is unequal; partial positive or negative charge ● Ion

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