| A | B |
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| In 1829, the German chemist _____ discovered that many elements could be grouped into set of three. | J.W. Dobereiner |
| Dobereiner's sets of three were called _____ | triads |
| Triads of elements tended to have similar _____ | properties |
| Not all know elements fall easily into a triad, so Dobereiner's _____ | classification scheme was abandoned |
| In 1869, the Russian chemist _____ published the first periodic table. | Dmitri Mendeleev |
| Mendeleev's table arranged elements by increasing _____ | atomic mass |
| In Mendeleev's periodic table, elements in the same _____ of the table had the most similar properties. | column |
| Blank spaces in the periodic table represented _____ | elements that had not yet been discovered |
| The properties of the undiscovered elements in Mendeleev's table could be predicted based on _____ | the elements in the same column |
| When Mendeleev created his periodic table, he did not know of the existence of _____ | protons |
| In 1913, _____ created the current periodic table. | the British physicist Henry Moseley |
| Moseley's periodic table is arranged by _____ | increasing atomic number |
| On the modern periodic talbe, horizontal rows are called _____ | periods |
| In the modern periodic table, vertical columns are called _____ | groups or columns |
| Elements in the same groups tend to have _____ | similar properties |
| The periodic law states _____ | when elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties. |
| Of protons, neutrons, or electrons, the one that plays the greatest role in determining the properties of an element is the _____ | protons |
| Nobel gases | inert gases; rarely take part in reactions; very stable; resistant to change |
| alkali metals | one electron in the highest occupied energy level, therefore highly reactive. Soft metals that can be cut with a knife. Produce alkaline solutions. Solid alkali metals are good conductors of electricity |
| Alkaline earth metals | harder, denser, stronger, higher melting points than the alkali metals; all are reactive. |
| Transition metals | have electrons in d orbitals; properties vary |
| Halogens | combine easily with metals, especially the alkali metals, to form salts. Most reactive non-metal elements; highest energy level is one electron short of being full. |
| Inner transition metals are made up of _____ and _____. | lanthanides and actinides |
| Lathanides are _____ | shiny, reactive metals; have electrons in the f orbitals |
| Actinides have _____ | unstable arrangement of protons and neutrons in the nucleus; all have radioactive forms; have electrons in the f orbitals |
| Representative metals _____ | represent the entire range of chemical properties |
| Metals _____ | are excellent conductors of heat and electricity; shiny, malleable (can be formed into shapes) and ductile (can be drawn out into wire) |
| Nonmetals _____ | are usually poor conductors of electricity and heat; most are gases or are brittle solids at room temperature |
| Metalloids _____ | have some properties of metals and some properties of nonmetals; some have moderate electrical conductivity |
| _____ is the only element which forms a group by itself. | hydrogen |
| Hydrogen is _____ | very reactive |
| The elements in each column have _____ | the same number of electrons in the last orbital |
| Valence electrons are _____ | the number of electrons an atom has in its outer shell |
| Valence electrons are important to the behavior of atoms because _____ | it determines how easily an atom reacts with another atom of a different element |
| The less electrons in the outer valence the _____ | less stable the atom is and the more likely it is to react |
| Atoms gain or lose electrons to have the same number of electrons as _____ | protons, creating a neutral atom which is stable |
| Why are the noble gases considered noble? | they do not react with other elements; they are very stable |
| The structure of noble gases that makes them so stable is _____ | their outer orbital is full |
| Why is hellium considered a noble gas? | It is stable and has its outer most orbital full |
