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  2. Atomicity (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Atomicity_(chemistry)

    For example, each molecule of oxygen (O 2) is composed of two oxygen atoms. Therefore, the atomicity of oxygen is 2. [1] In older contexts, atomicity is sometimes equivalent to valency. Some authors also use the term to refer to the maximum number of valencies observed for an element. [2]

  3. Effective atomic number (compounds and mixtures) - Wikipedia

    en.wikipedia.org/wiki/Effective_atomic_number...

    The effective atomic number is important for predicting how photons interact with a substance, as certain types of photon interactions depend on the atomic number. The exact formula, as well as the exponent 2.94, can depend on the energy range being used.

  4. Empirical formula - Wikipedia

    en.wikipedia.org/wiki/Empirical_formula

    In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms present in a compound. [1] A simple example of this concept is that the empirical formula of sulfur monoxide , or SO, is simply SO, as is the empirical formula of disulfur dioxide , S 2 O 2 .

  5. Oxygen - Wikipedia

    en.wikipedia.org/wiki/Oxygen

    2 combines with atomic oxygen made by the splitting of O 2 by ultraviolet (UV) radiation. [22] Since ozone absorbs strongly in the UV region of the spectrum, the ozone layer of the upper atmosphere functions as a protective radiation shield for the planet. [22] Near the Earth's surface, it is a pollutant formed as a by-product of automobile ...

  6. List of CAS numbers by chemical compound - Wikipedia

    en.wikipedia.org/wiki/List_of_CAS_numbers_by...

    This is a list of CAS numbers by chemical formulas and chemical compounds, indexed by formula.The CAS number is a unique number applied to a specific chemical by the Chemical Abstracts Service (CAS).This list complements alternative listings to be found at list of inorganic compounds and glossary of chemical formulae

  7. List of chemistry mnemonics - Wikipedia

    en.wikipedia.org/wiki/List_of_chemistry_mnemonics

    Number of consonants denotes number of oxygen atoms. Number of vowels denotes negative charge quantity. Inclusion of the word "ate" signifies that each ends with the letters a-t-e. To use this for the -ite ions, simply subtract one oxygen but keep the charge the same.

  8. Atomic number - Wikipedia

    en.wikipedia.org/wiki/Atomic_number

    The atomic number can be used to uniquely identify ordinary chemical elements. In an ordinary uncharged atom, the atomic number is also equal to the number of electrons. For an ordinary atom which contains protons, neutrons and electrons, the sum of the atomic number Z and the neutron number N gives the atom's atomic mass number A.

  9. Oxygen compounds - Wikipedia

    en.wikipedia.org/wiki/Oxygen_compounds

    Oxygen is present as compounds in the atmosphere in trace quantities in the form of carbon dioxide (CO 2) and oxides of nitrogen (NO x). The Earth's crustal rock is composed in large part of oxides of silicon (silica SiO 2, found in granite and sand), aluminium (aluminium oxide Al 2 O 3, in bauxite and corundum), iron (iron (III) oxide Fe 2 O