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  2. Mixture - Wikipedia

    en.wikipedia.org/wiki/Mixture

    Mixture. A mixture is a material made up of two or more different chemical substances which can be separated by physical method. [1] A mixture is the physical combination of two or more substances in which the identities are retained and are mixed in the form of solutions, suspensions and colloids. [2][3]

  3. Chemical substance - Wikipedia

    en.wikipedia.org/wiki/Chemical_substance

    A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. [1][2] Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combined without reacting, they may form a chemical mixture. [3]

  4. Chemical compound - Wikipedia

    en.wikipedia.org/wiki/Chemical_compound

    Any substance consisting of two or more different types of atoms (chemical elements) in a fixed stoichiometric proportion can be termed a chemical compound; the concept is most readily understood when considering pure chemical substances. [10]: 15 [11] [12] It follows from their being composed of fixed proportions of two or more types of atoms ...

  5. Covalent bond - Wikipedia

    en.wikipedia.org/wiki/Covalent_bond

    Covalent bond. A covalent bond forming H 2 (right) where two hydrogen atoms share the two electrons. A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...

  6. Diatomic molecule - Wikipedia

    en.wikipedia.org/wiki/Diatomic_molecule

    Diatomic molecule. Diatomic molecules (from Greek di- 'two') are molecules composed of only two atoms, of the same or different chemical elements. If a diatomic molecule consists of two atoms of the same element, such as hydrogen (H2) or oxygen (O2), then it is said to be homonuclear. Otherwise, if a diatomic molecule consists of two different ...

  7. Chemical reaction - Wikipedia

    en.wikipedia.org/wiki/Chemical_reaction

    A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. [1] When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an energy change as new products are generated. Classically, chemical reactions encompass changes that only involve the positions ...

  8. Molecule - Wikipedia

    en.wikipedia.org/wiki/Molecule

    A pure substance is composed of molecules with the same average geometrical structure. The chemical formula and the structure of a molecule are the two important factors that determine its properties, particularly its reactivity. Isomers share a chemical formula but normally have very different properties because of their different structures.

  9. Law of definite proportions - Wikipedia

    en.wikipedia.org/wiki/Law_of_definite_proportions

    In chemistry, the law of definite proportions, sometimes called Proust's law or the law of constant composition, states that a given chemical compound always contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation. For example, oxygen makes up about 8 / 9 of the mass of any sample of ...