 | Term | Definition |
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Dimitri Mendeleev |
discovered a pattern to the elements in 1869. He arranged them by properties |
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periodic |
happening at regular intervals |
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Mendeleev's periodic table |
periodic table of elements |
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periodic law |
law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements |
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Henry Moseley |
determined the number of protons-atomic number-in an atom |
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metals, nonmetals, and metalloids |
elements are classified by... |
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metals |
these are to the left side of the zig zag line on the periodic table; they usually have few electrons in their outer energy level; they are usually solid at room temperature |
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metals |
they are shiny, ductile, malleable, good conductors of thermal energy |
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nonmetals |
not malleable, not ductile, not shiny, poor conductors of thermal energy and electric current |
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nonmetals |
found to the right of the zig zag line on the periodic table; have almost a complete set of electrons on their outer energy level |
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metalloids |
semiconductors; border the zigzag line on the periodic table; have about half of a complete set of electrons in their outer energy level |
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metalloids |
shiny, brittle, hard, good conductor of electric current |
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period |
horizontal rows on the periodic table |
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group |
vertical column on the periodic table |
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family |
group |
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alkali metals |
elements of group 1 ; metals; very reactive; softness; color of silver; shininess; low density; easily give away one electron from their outer energy level |
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alkaline-earth metal |
elements in group 2 ; metals; very reactive but less reactive than alkali metals; but higher densities; two electrons in the outer energy level |
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transition metals |
elements in groups 3-12 ; metals; 1 or 2 electrons in their outer energy level; less reactive; good conductors of thermal energy; shiny; |
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lanthanides |
shiny, reactive metals in the transition metals used to make steels |
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actinides |
radioactive, unstable elements in transition metals |
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carbon group |
group 14 ; made of one nonmetal; two metalloids; and two metals; four electrons in the outer energy level; solid at room temperature |
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nitrogen group |
group 15 ; made of two nonmetals, two metalloids; and one metal; solid at room temperature |
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oxygen group |
group 16; contains three nonmetals; one metalloid; one metal; there are 6 electrons in its outer energy level ; reactive; all but oxygen are solid at room temperature |
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halogens |
group 17; contains nonmetals; 7 electrons in its outermost energy level; very reactive; poor conductors of electric current; never in its uncombined form in nature; combine with most metals to form salts |
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noble gases |
group 18; nonmetals; 8 electrons in its outermost energy level; unreactive; colorless odorless; gases at room temperature |
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hydrogen |
one electrons in its outermost energy level; reactive; colorless, odorless, gas at room temperature, low density, explosive reactions with oxygen |
