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| 33476647 | matter | anything that takes up space and has mass | |
| 33476648 | element | a substance that cannot be broken down to other substances by chemical reactions | |
| 33476649 | 92 | How many elements occur in nature? | |
| 33476650 | compound | a chemical substance that consists of two or more elements combined in a fixed ratio | |
| 33476651 | 25 | How many elements are essential for life? | |
| 33476652 | carbon, hydrogen, nitrogen, oxygen | Ninety-six percent of all the matter in living organisms is composed of what four elements? (alphabetical order) | |
| 33476653 | trace element | elements required by an organism in minute quantities; examples in humans are boron and iodine | |
| 33476654 | proton | electric charge = 1+, location in atom=nucleus, mass in Daltons ~ 1 | |
| 33476655 | neutron | electric charge = neutral, location in atom=nucleus, mass in Daltons ~ 1 | |
| 33476656 | electron | electric charge = 1-, location in atom = electron cloud (around nucleus), mass in Daltons ~ 1/2000 | |
| 33476657 | proton | Which type of subatomic particle must be the same in number for all atoms of the same element? | |
| 33476658 | atomic number | the number of protons contained in the nuclei of all atoms of a particular element | |
| 33476659 | mass number | a number representative of the sum of the protons plus neutrons in an atom's nucleus | |
| 33476660 | isotopes | different atomic forms of an element that have more neutrons, and therefore a greater mass, than other atoms of the same element | |
| 33476661 | non-radioactive isotopes | type of isotope that reacts only when combined with atoms of another element | |
| 33476662 | radioactive isotopes | type of isotope have spontaneously-decaying nuclei, allowing for the constant release of particles and energy | |
| 33476663 | radioactive isotopes | uses of these include: 1) tracers to follow atoms through metabolism or other chemical processes within an organism; 2) used as tracers in diagnostic methods by injecting them into blood and measuring amount of tracer later excreted; 3) used to determine date/age of fossils | |
| 33476664 | electrons | Which subatomic particles are directly involved in the chemical reactions between atoms? | |
| 33476665 | farther away | Which has more potential energy, an electron close to the nucleus or one farther away? | |
| 33476666 | releases energy | If an electron falls from a higher shell to a lower one, does the electron absorb energy or release energy? | |
| 33476667 | outermost | How an atom behaves chemically mostly depends on the number of electrons in the atom's ____________ shell. | |
| 33476668 | orbital | the three-dimensional space in which an electron is found 90% of the time | |
| 33476669 | chemical bond | an attraction that exists between atoms after they either share or transfer their valence electrons | |
| 33476670 | covalent bond | the sharing of a pair of valence electrons by two atoms; considered a strong bond in biology | |
| 33476671 | ionic bond | the attraction that exists between opposing (positive and negative) charges within the atom | |
| 33476672 | molecule | the composition that results from two or more atoms being held together by a covalent bond | |
| 33476673 | single covalent bond | type of bond that exists when two atoms share a pair of electrons; weakest form of this type of bond | |
| 33476674 | double covalent bond | type of bond that exists when two atoms share two pairs of electrons; second strongest form of this type of bond | |
| 33476675 | triple covalent bond | type of bond that exists when two atoms share three pairs of electrons; strongest form of this type of bond | |
| 33476676 | structural formula | diagram that illustrates the pairing and sharing of electrons between two atoms | |
| 33476677 | molecular formula | diagram that demonstrates the number of atoms within a given molecule | |
| 33476678 | electronegativity | the attraction that exists between a particular type of atom because of the electrons involved in a covalent bond | |
| 33476679 | nonpolar covalent bond | in this type of bond, the electrons are shared equally between two atoms | |
| 33476680 | polar covalent bond | in this type of bond, the electrons are shared unequally between two atoms | |
| 33476681 | ion | a charged atom or molecule | |
| 33476682 | cation | a positively charged ion | |
| 33476683 | anion | a negatively charged ion | |
| 33476684 | hydrogen bond | the type of bond that is formed when a hydrogen atom that is already bonded to one electronegative atom is also attracted to another electronegative atom | |
| 33476685 | van der Waal bonds | the type of bonding that occurs when atoms and molecules are close in proximity, and are the result of constantly changing regions of positive and negative charge that enable them to stick together | |
| 33476686 | tetrahedron | shape of molecule that results from 4 bonded atoms | |
| 33476687 | bent, pyramid | shapes of molecule that results from 3 bonded atoms | |
| 33476688 | linear | shape of molecule that results from 2 bonded atoms | |
| 33476689 | chemical equilibrium | the point at which the forward and reverse reactions in a chemical reaction offset each other, thus diminishing their effects on the reactants involved |
