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  2. Chemical compound - Wikipedia

    en.wikipedia.org/wiki/Chemical_compound

    [16] [17] [18] A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with two atoms in the oxygen molecule (O 2); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (two hydrogen atoms and one oxygen atom; H 2 O). A molecule is the smallest unit of a substance that ...

  3. Chemical substance - Wikipedia

    en.wikipedia.org/wiki/Chemical_substance

    The majority of elements are classified as metals. These are elements with a characteristic lustre such as iron, copper, and gold. Metals typically conduct electricity and heat well, and they are malleable and ductile. [11] Around 14 to 21 elements, [12] such as carbon, nitrogen, and oxygen, are classified as non-metals.

  4. Chemical composition - Wikipedia

    en.wikipedia.org/wiki/Chemical_composition

    A chemical composition specifies the identity, arrangement, and ratio of the chemical elements making up a compound by way of chemical and atomic bonds.. Chemical formulas can be used to describe the relative amounts of elements present in a compound.

  5. Chemical element - Wikipedia

    en.wikipedia.org/wiki/Chemical_element

    A chemical element is a chemical substance whose atoms all have the same number of protons.The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8, meaning each oxygen atom has 8 protons in its nucleus.

  6. Molecule - Wikipedia

    en.wikipedia.org/wiki/Molecule

    A compound's empirical formula is a very simple type of chemical formula. [27] It is the simplest integer ratio of the chemical elements that constitute it. [28] For example, water is always composed of a 2:1 ratio of hydrogen to oxygen atoms, and ethanol (ethyl alcohol) is always composed of carbon, hydrogen, and oxygen in a 2:6:1 ratio.

  7. Glossary of chemistry terms - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_chemistry_terms

    3. Colloquially, any compound which, when dissolved in water, yields a pH of less than 7.0. The term "acid" is commonly used to refer to the entire aqueous solution, whereas stricter definitions refer only to the acidic solute. [2] acid anhydride Any chemical compound derived by the removal of water molecules from an acid. Contrast base anhydride.

  8. Chemistry - Wikipedia

    en.wikipedia.org/wiki/Chemistry

    A compound is a pure chemical substance composed of more than one element. The properties of a compound bear little similarity to those of its elements. [22] The standard nomenclature of compounds is set by the International Union of Pure and Applied Chemistry (IUPAC). Organic compounds are named according to the organic nomenclature system. [23]

  9. Chemical formula - Wikipedia

    en.wikipedia.org/wiki/Chemical_formula

    In chemistry, the empirical formula of a chemical is a simple expression of the relative number of each type of atom or ratio of the elements in the compound. Empirical formulae are the standard for ionic compounds , such as CaCl 2 , and for macromolecules, such as SiO 2 .