AP Bio - Chapter 2
Terms
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- Element
- A fundamental form of matter that has mass, takes up space, and cannot be broken down into something else on Earth.
- Atoms
- particles that retain the properties of an element.
- Protons
- Positive charge, one in every atom.
- Neutrons
- No charge, one in every atom.
- Nucleus
- Core of atoms; protons and neutrons
- Electrons
- Negative charge, normally equal amounts of electrons and protons.
- Atomic number
- Number of protons in each atom.
- Mass number
- Combined number of neutrons and protons.
- Isotopes
- Atoms that vary in neutron number.
- Radioisotope
- Isotope with unstable nucleus, stabilizes by emitting energy and particles.
- Radioactive decay
- Transforms a radioisotope into a new element.
- Tracers
- Substances with an isotope attached to them (often radioisotopes).
- Radiation therapy
- Radioisotopes stop activity of abnormal body cells.
- Orbital
- Space around nucleus in which electrons are likely to be found.
- Shell model
- A “shell†encloses all orbitals available to electrons at the same energy level.
- Inert atoms
- Atoms with no vacancies.
- Chemical bond
- Union between electron structures of atoms.
- Molecule
- Two or more bonded atoms.
- Diatomic molecules
- Molecules with two of the same element.
- Compounds
- Molecules with elements in proportions that never vary.
- Mixture
- Two or more elements or compounds intermingled in proportions that usually vary.
- Ionic bond
- Association of two ions with opposing charges.
- Ion
- Atom that has either lost or received an electron (charged).
- Covalent bond
- sharing of a pair of electrons between two atoms.
- Non-polar covalent bond
- No difference in change between ends of bond, atoms share electrons equally.
- Polar covalent bond
- More attractive (electronegative atom) exerts stronger pull on electrons --> slightly negative (No molecular net charge).
- Hydrogen bond
- Weak attraction between an electronegative atom and a hydrogen atom taking part in a second polar covalent bond.
- Hydrophilic substances
- Polar substances, attracted to water.
- Hydrophobic substances
- Non-polar molecules, repel hydrophilic substances and water.
- Temperature
- Measure of molecular motion.
- Cohesion
- Capacity to resist rupturing when placed under tension.
- “Spheres of Hydrationâ€
- Formed when water molecules cluster around oppositely charged solute (dissolved substances) ions or molecules
- pH scale
- Determines H+ concentration in liquids.
- Neutrality
- pH = 7, pure water, [H=] = [OH-]
- Acids
- pH = 0-7, proton donators (lemon juice, coffee)
- Bases
- pH = 7-14, proton acceptors (seawater, baking soda, “alkaline†fluids).
- Salts
- Compounds that release ions other than H= and OH- in solutions.