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Chemistry

Science Review of Metalloids

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Overview Metalloids are elements that have some properties of metals and some of nonmetals.  They are on the periodic table along the dividing line between metals and nonmetals. The most commonly recognized metalloids include the elements boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te). Metalloids Elements are commonly classified as…

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Science Review of Mercury

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Overview The element mercury (Hg) has atomic number 80, and is considered a transition metal.  It is liquid at room temperature.  Although mercury is highly toxic, it is a good electrical conductor, and is used in some electrical switches. Properties of Mercury Mercury is the only metal that is liquid at room temperature.  It is…

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Science Review of Transition Metals

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Overview The transition metals occupy a large area on the periodic table.  They all appear to have similar metallic properties, because of the way their electron shells are filled.   Many transition metals form brightly colored compounds, especially in solution.  The transition metal group includes common elements such as iron (Fe), copper (Cu), nickel (Ni), gold…

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Science Review of Alkaline Earth Metals

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Overview The alkaline earth metals are the next column in the periodic table from the alkaline metals. They include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). They have two electrons in their outermost shell, which they give up in chemical reactions. Beryllium (Be) Beryllium (atomic number 4) is a…

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Science Review of Alkali Metals

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Overview The alkali metals are in Group 1 of the periodic table.  They include the elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).  These highly reactive elements form compounds easily and explosively.  They all have one electron in their outermost shell, giving it up to form ionic compounds. Lithium…

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Science Review of Chemical Equations

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Overview Chemical equations are shorthand descriptions of the reactions between substances.  They include the chemicals that react, the conditions for reaction, the products of the reaction, and the amounts of all substances involved. Word Equations In the simplest form, chemical equations can be expressed in words.  For example, the substance methane reacts with oxygen to…

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Science Review of Compounds

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Overview Chemical elements are often found within chemical compounds, in which one or more elements are bonded together.  Some elements exist freely in compounds with one another, while others are bonded by electrostatic charges and still others are bonded with molecular bonds. Molecules A molecule is the smallest uncharged unit of a compound, containing at…

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Science Review of Hydrogen Isotopes

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Overview The element hydrogen is the lightest of all elements in the periodic table, with one proton in its nucleus. It is also the most abundant element in the universe.  Hydrogen has 3 naturally occurring isotopes, although others have been produced experimentally. Hydrogen The most common form of hydrogen has one proton in its nucleus…

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Science Review of Stellar Structure and Nuclear Reactions inside Stars

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Overview The nuclear energy that powers stars depends upon the core temperature and the available fuel. During the main-sequence phase for most stars, nuclear fusion of 4 hydrogen atoms to form 2 helium atoms provides the most energy. Other types of fusion reactions occur in stars with higher core temperatures and when hydrogen fuel is…

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Chemistry Review of Substances and Mixtures

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Overview Substances occur in elements or compounds, while mixtures can be any combination of one or more elements or compounds. Mixtures may occur as solutions or heterogeneous combinations. Elements and Compounds Elements and compounds are known as pure substances. A molecule of one of the elements or compounds only contains that substance. For example, a…

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