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Life Chapter 2
Sadava / Life 9e Chapter 2 Key Terms
| Term | Definition |
|---|---|
| isotope (eye′ so tope) | 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. |
| mass number | The sum of the number of protons and neutrons in an atom's nucleus. |
| Mole | 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: 6.023 x 1023 molecules. |
| molecular weight | The sum of the atomic weights of all the atoms in a molecule. |
| Molecule | A chemical substance made up of two or more atoms joined by covalent bonds or ionic attractions. |
| neutron (new′ tron) | One of the three fundamental particles of matter (along with protons and electrons), with mass approximately 1 amu and no electrical charge. |
| nucleus (new′ klee us) | (1) In cells, the centrally located compartment of eukaryotic cells that is bounded by a double membrane and contains the chromosomes. (2) In the brain, an identifiable group of neurons that share common characteristics or functions. |
| Orbital | A region in space surrounding the atomic nucleus in which an electron is most likely to be found. |
| pH | 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. |
| Polar | Having separate and opposite electric charges at two ends, or poles. (Contrast with nonpolar.) |
| proton (pro′ ton) | (1) A subatomic particle with a single positive charge. The number of protons in the nucleus of an atom determine its element. (2) A hydrogen ion, H+. |
| radioisotope | A radioactive isotope of an element. Examples are carbon-14 (14C) and hydrogen-3, or tritium (3H). |
| reactant | A chemical substance that enters into a chemical reaction with another substance. |
| reversible reaction | A chemical change that can occur in both the forward and reverse directions. |
| Solute | A substance that is dissolved in a liquid (solvent) to form a solution. |
| Solution | A liquid (the solvent) and its dissolved solutes. |
| Solvent | Liquid in which a substance (solute) is dissolved to form a solution. |
| specific heat | The amount of energy that must be absorbed by a gram of a substance to raise its temperature by one degree centigrade. By convention, water is assigned a specific heat of one. |
| van der Waals forces | 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. |
| Acid | A substance that can release a proton in solution. (Contrast with base.) |
| anion (an′ eye on) | A negatively charged ion. |
| atom | The smallest unit of a chemical element. Consists of a nucleus and one or more electrons. |
| atomic number | 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. |
| atomic weight | 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. |
| Avogadro's number | The number of atoms or molecules in a mole (weighed out in grams) of a substance, calculated to be 6.022 x 1023. |
| Base | (1) A substance that can accept a hydrogen ion in solution. (Contrast with acid.) (2) In nucleic acids, the purine or pyrimidine that is attached to each sugar in the sugar–phosphate backbone. |
| Buffer | A substance that can transiently accept or release hydrogen ions and thereby resist changes in pH. |
| cation (cat′ eye on) | An ion with one or more positive charges. (Contrast with anion.) |
| chemical bond | An attractive force stably linking two atoms. |
| chemical reaction | The change in the composition or distribution of atoms of a substance with consequent alterations in properties. Usually involve changes in the distribution of electrons between atoms. |
| Cohesion | The tendency of molecules (or any substances) to stick together. |
| Compound | (1) A substance made up of atoms of more than one element. |
| covalent bond | Chemical bond based on the sharing of electrons between two atoms. |
| electron shell | The region surrounding the atomic nucleus at a fixed energy level in which electrons orbit. |
| Electron | A subatomic particle outside the nucleus carrying a negative charge and very little mass. |
| Electronegativity | The tendency of an atom to attract electrons when it occurs as part of a compound. |
| Element | 1.A substance that cannot be converted to simpler substances by ordinary chemical means.2. a pure substance that contains only 1 kind of atom. |
| Energy | The capacity to do work or move matter against an opposing force. The capacity to accomplish change in physical and chemical systems. |
| heat of vaporization | The energy that must be supplied to convert a molecule from a liquid to a gas at its boiling point. |
| hydrogen bond | 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. |
| hydrophilic (high dro fill′ ik) | Having an affinity for water. (Contrast with hydrophobic.) |
| hydrophobic (high dro foe′ bik) | no affinity for water. Uncharged and nonpolar groups of atoms are hydrophobic. (Contrast with hydrophilic.) |
| ion (eye′ on) | An electrically charged particle that forms when an atom gains or loses one or more electrons. |
| ionic bond | An electrostatic attraction between positively and negatively charged ions. |
| Mass | A measure of the quantity of matter present |
| Dalton | The mass of a proton serves as a standard unit of measure (atomic mass unit (amu)) |
| Radioactive Decay | When unstable isotopes give off energy in the form of alpha, beta, or gamma radiation from the atomic nucleus, and transforms the original atom |
| Orbital | A region in space surrounding the atomic nucleus in which an electron is most likely to be found. |
| Valence Shell | The outer most electron shell and determines how the atoms combines with other atoms. |
| Stable | When valence shell has no unpaired electrons and it will not react with other atoms. |
| Bonded | When radioactive atoms attain stability by sharing electrons w/other atoms or by losing or gaining electrons the atoms involved are called this. |
| Octet rule | the tendency of atoms to form stable molecules so that they have eight electrons in their outer most shell. |
| Ionic Bonds | Bond that forms when an atom gains or loses on or more electrons to achieve stability |
| Single Bond | Involves the sharing of a single pair of electrons (ex H-H or C-H) |
| Double Bond | Involves the sharing of 4 electrons (two pairs) (C=C) |
| Triple Bond | Six shared electrons are rare. |
| Nonpolar Covalent Bond | when two atoms are close in electronegativity they will share electrons equally |
| Polar Covalent Bond | When electrons are drawn to one nucleus more than to the other |
| complex Ions | Groups of covently bonded atoms that carry an electric charge |
| Chemical Reaction | Occures when moving atoms collide with sufficient energy to combine or change their bonding partner. |
| Product | The outcome of reactants |
| Heat of Vaporization | The energy that must be supplied to covert a molecule from liquid to a gas at its boiling point |
| Cohesion | The tendency of molecules (or any substance) to stick together. |
| Aqueous Solution | if the solvent is water |
| Qualitative Analyses | deal w/the indentification of substances involved in chemical reactions |
Created by:
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