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Definition
| Anything that occupies space and has mass. |
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| A substance that cannot be broken down to other substances by ordinary chemical means. There are 92 in nature, and 25 are essential to life. |
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| Which four elements make up 96% of life? |
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Definition
| Carbon, Oxygen, Hydrogen, Nitrogen |
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| Substance consistingof two or more different elements combined in a fixed ratio. Much more common than pure element. Example: NaCl (Sodium Chloride) |
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| Means "indivisible" and is the smallest unit of matter that still retains the properties of an element. |
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| Proton, Neutron, Electron |
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Definition
| Protons and neutrons are in nucleus of atom. Protons are positive, electrons are negative, and neutrons are neutral. |
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Definition
| The number of protons in an atom, which stays constant. Unless otherwise indicated, the number of protons equals the number of electrons. |
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Definition
| The sum of the number of protons and neutrons in an atoms nucleus. |
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Definition
| Equal to the mass number, which is the sum of protons and neutrons. |
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Definition
| The isotopesof an element have the same number of protons and electrons and behave identically in chemical reactions, but they have different numbers of neutrons. |
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Definition
| One in which the nucleus decays spontaneously, giving off particles and energy. Carbon 14 is an example. |
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Definition
| Different energy levels of electrons. Depending on its atomic number, an atom may have multiple shells around the nucleus. You can tell how many shells by the rows on the periodic table. |
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Definition
| When two atoms with incomplete outer shells react, and each atom either shares, donates, or receives outer electrons, so that both partners end up with completed shells. |
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Definition
| An atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons. |
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Definition
| When two ions with opposite charges attract each other and create a neutral compound. |
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Definition
| A chemical bond in which two atoms share one or more pairs of outer shell electrons. Two or more atoms held together by covalent bonds form a molecule. |
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Definition
| An atoms attraction for shared electrons. |
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Definition
| Electrons are shared equally between atoms (equal electronegativty) Examples are methan (CH4) and O2, H2 |
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Term
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Definition
| Unequal distribution of charges. The pulling of shared, negatively charged electrons closer to the more electronegative atom makes one atom partially negative and the other atom partially positive. |
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Definition
| A weaker bond that is crucial to the functioning of a cell between molecules. Occurs as a part of polar covalent bonds, when the negative charged region becomes attractived to a positively charged hydrogen ion. |
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Definition
| The tendency of molecules to stick together. Much stronger in water than for most other liquids. |
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Term
| Why does ice float on top of liquid water? |
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Definition
| Because it is less dense. As water freezes, the hydrogen molecules become stable in their bonds, holding each other at arms length. In liquid water, the bonds constantly break and reform. |
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Term
| On the pH scale, what characterizes 1-6? |
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Definition
| Higher concentration of H+, becoming increasingly acidic as you go down. |
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| On the pH scale, what charcterizes 8-14? |
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Definition
| Lower concentraton of H+, becoming more basic. |
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Term
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Definition
| Substances that minimize changes in pH. They do so by accepting H+ when it is in excess and donating H+ when it is depleted. Examples are antacids. |
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Term
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Definition
| The making and breaking of chemical bonds |
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