Bio 20A, Chapter 2., Small Molecules And The Chemistry Of Life

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atom

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The smallest unit of a chemical element. Consists of a nucleus and one or more electrons.

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electron

Back 2

A subatomic particle outside the nucleus carrying a negative charge and very little mass.

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proton

Back 3

A subatomic particle with a single positive charge. The number of protons in the nucleus of an atom determine it's element. Also, the hydrogen ion, H+.

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neutron

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One of the three fundamental particles of matter (along with protons and electrons), with mass approximately 1 amu and no electrical charge.

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atomic mass unit (amu)

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the mass of a proton or neutron, which serves as a standard unit of measurement.

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element

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A substance that cannot be converted to simpler substances by ordinary chemical means.

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atomic number

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The number of protons in the nucleus of an atom; also equals the number of electrons around the neutral atom. Determines the chemical properties of the atom.

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mass number

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The sum of the number of protons and neutrons in an atom's nucleus.

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isotope

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Isotopes of a given chemical element have the same number of protons in their nuclei (and thus are in the same position on the periodic table), but differ in the number of neutrons.

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atomic weight

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The average of the mass numbers of a representative sample of atoms of an element, with all the isotopes in their normally occurring proportions. Also called atomic mass.

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radioisotope

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A radioactive isotope of an element. Examples are carbon-14 and hydrogen-3 (tritium).

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molecule

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A chemical substance made up of two or more atoms joined by covalent bonds or ionic attractions.

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orbital

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A region in space surrounding the atomic nucleus in which an electron is most likely to be found.

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electron shell

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The region surround the atomic nucleus at a fixed energy level in which electrons orbit.

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chemical bond

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An attractive force stably linking two atoms.

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covalent bond

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Chemical bond based on the sharing of electrons between two atoms.

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compound

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A substance made up of atoms of more than one element.

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What is the chemical formula for table sugar?

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C12H22O11

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What is table sugar?

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sucrose

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molecular weight

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The sum of the atomic weights of the atoms in a molecule.

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electronegativity

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The tendency of an atom to attract electrons when it occurs as part of a compound.

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polar

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Having separate and opposite electric charges at two ends, or poles.

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ion

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An electrically charged particle that forms when an atom gains or loses one or more electrons.

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cation

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An ion with one or more positive charges.

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anion

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A negatively charged ion.

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ionic bond

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An electrostatic attraction between positively charged and negatively charged ions.

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Chemical formula for ammonium

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NH4+

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Chemical formula for sulfate

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SO4²-

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Chemical formula for phosphate

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PO4³-

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hydrogen bond

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A weak electrostatic bond which arises from the attraction between the slight positive charge on a hydrogen atom and a slight negative charge on a nearby oxygen or nitrogen atom; not restricted to water molecules..

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hydrophilic

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Having an affinity for water.

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hydrophobic

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Having no affinity for water. Uncharged and nonpolar groups of atoms are hydrophobic. (May be more attracted to one another than to water).

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van der Waals forces

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Weak attractions between atoms resulting from the interaction of the electrons of one atom with the nucleus of another. This type of attraction is about one-fourth as strong as a hydrogen bond. May be encouraged by the 'herding' of hydrophobic molecules.

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chemical reaction

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The change in the composition or distribution of atoms of a substance with consequent alterations in properties.

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reactant

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A chemical substance that enters into a chemical reaction with another substance.

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What are 5 important properties of water?

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less dense when in a solid state, has a high heat capacity, a high heat of vaporization, strong cohesive strength, and high surface tension.

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heat capacity

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the amount of heat required to change a body's temperature by a given amount.

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What is the symbol for heat capacity?

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C

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energy

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The capacity to do work or move matter against an opposing force. The capacity to accomplish change in physical and chemical systems.

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specific heat

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The amount of energy that must be absorbed by a gram of substance to raise its temperature by one degree centigrade. By convention, water is assigned a specific heat of one.

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heat of vaporization

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The energy that must be supplied to convert a molecule from a liquid to a gas at its boiling point.

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cohesion

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The tendency of molecules (or any substances) to stick together.

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solution

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A liquid (the solvent) and its dissolved solutes.

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solute

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A substance that is dissolved in a liquid (solvent) to form a solution.

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solvent

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Liquid in which a substance (solute) is dissolved to form a solution.

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aqueous solution

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a solution where the solvent is water.

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mole

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A quantity of a compound whose weight in grams is numerically equal to its molecular weight expressed in atomic mass units. Avogadro's number of molecules: 6.022e23 molecules.

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Avogadro's number

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The number of atoms or molecules in a mole (weighed out in grams) of substance, calculated to be 6.022e23.

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acid

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A substance that can release a proton in solution. Those that fully ionize in water are called strong acids.

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base

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A substance that can accept a hydrogen ion in solution.

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reversible reaction

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a chemical reaction that can proceed in either direction, left to right or right to left, depending on the relative starting concentrations of the reactants and products.

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pH

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The negative logarithm of the hydrogen ion concentration; a measure of the acidity of a solution. A solution with pH = 7 is said to be neutral; pH values higher than 7 characterize basic solutions, while acidic solutions have pH values less than 7.

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buffer

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A substance that can transiently accept or release hydrogen ions and thereby resist change in pH.

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homeostasis

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the maintenance of a steady state, such as a constant temperature or a stable social structure, by means of physiological or behavioral feedback responses.

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dalton

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1 amu

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What the symbol for a dalton?

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Da