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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. Group (periodic table) - Wikipedia

    en.wikipedia.org/wiki/Group_(periodic_table)

    In chemistry, a group (also known as a family) [1] is a column of elements in the periodic table of the chemical elements. There are 18 numbered groups in the periodic table; the 14 f-block columns, between groups 2 and 3, are not numbered.

  4. Chalcogen - Wikipedia

    en.wikipedia.org/wiki/Chalcogen

    Out of the six known chalcogens, one (oxygen) has an atomic number equal to a nuclear magic number, which means that their atomic nuclei tend to have increased stability towards radioactive decay. [13] Oxygen has three stable isotopes, and 14 unstable ones. Sulfur has four stable isotopes, 20 radioactive ones, and one isomer.

  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. 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.

  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. Allotropes of oxygen - Wikipedia

    en.wikipedia.org/wiki/Allotropes_of_oxygen

    There are several known allotropes of oxygen. The most familiar is molecular oxygen (O 2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O 3). Others are: Atomic oxygen (O 1), a free radical. Singlet oxygen (O * 2), one of two metastable states of ...

  9. Atomic radii of the elements (data page) - Wikipedia

    en.wikipedia.org/wiki/Atomic_radii_of_the...

    Atomic radii vary in a predictable and explicable manner across the periodic table. For instance, the radii generally decrease rightward along each period (row) of the table, from the alkali metals to the noble gases; and increase down each group (column). The radius increases sharply between the noble gas at the end of each period and the ...