Biology Section 2
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45 terms
Terms | Definitions |
|---|---|
 Matter | anything that occupies space and has mass |
| Matter's 3 forms | solid, liquid, water |
| element | substance that cannot be broken down to other substances by ordinary chemical means |
| compound | substance consisting of two or more different elements combined in a fixed ratio |
| Few elements | exist in a pure state |
| A compound has characteristics | different from its own elements |
| Four essential elements | oxygen, hydrogen, carbon, and nitrogen |
| Trace elements | essential but only in minute qualities |
| Some trace elements | are needed by all forms of life like iron |
| Iodine is essential | hormone production in the thyroid gland |
| Iodine deficiency | linked to mental retardation |
| Vitamins | consist of more than one element and are compounds |
| atom | the smallest unit of matter that is still an element |
| proton | subatomic particle with a positive charge |
| electron | subatomic particle with a negative charge |
| neutron | subatomic charge with a neutral charge |
| nucleus | atom's central core |
| The attraction between protons and electrons | holds the electrons near the nucleus |
| All atoms of a particular element | have the same unique number of protons |
| Atomic number | number of protons |
| Mass Number | the sum of the number of neutrons and protons in an atomic nucleus |
| Isotopes | atoms of the same element that differ in the number of neutrons they contain |
| Radioactive isotopes | Atoms that are unstable, meaning they decay, or break down, to form stable atoms of a different element |
| Biologists use radioactive tracers | to follow molecules as they undergo chemical changes |
| Only electrons | are directly involved in the chemical activity of an atom |
| Electron Shells | an energy level representing the distance of an electron from the nucleus of an atom. |
| Each orbital can only hold | 2 electrons |
| When two atoms with incomplete outer shells react | each atoms will send or recieve an electron |
| Chemical bond | hold atoms together |
| Covalent bond | strongest kind of bond; two atoms share one or more pairs of outer shell electrons; forms a molecule |
| Valence | the number of electrons in the outermost energy level of an atom |
| electronegativity | (chemistry) the tendency of an atom or radical to attract electrons in the formation of an ionic bond |
| nonpolar covalent bonds | electrons are shared equally between atoms |
| polar covalent bond | a covalent bond in which electrons are not shared equally |
| Polar molecule | unequal distribution of charges |
| Ion | atom that has a positive or negative charge that results from a gain or loss of electrons |
| Ionic bond | a chemical bond in which one atom loses an electron to form a positive ion and the other atom gains to electron to form a negative ion |
| Hydrogen bond | weak chemical bond formed by the attraction of positively charged hydrogen atoms to other negatively charged atoms |
| The structure of atoms and molecules | determine the way they behave |
| chemical reaction | breaking down and making of chemical bonds; leads to changes in the composition of matter |
| reactants | the elements or compounds that enter into a chemical reaction |
| product | material resulting from a chemical reaction |
| Cohesion | (physics) the intermolecular force that holds together the molecules in a solid or liquid |
| Adhesion | the property of sticking together (as of glue and wood) or the joining of surfaces of different composition |
| surface tension | a measure of how difficult it is to stretch or break the surface of a liquid |
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