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  2. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    The periodic table and law are now a central and indispensable part of modern chemistry. The periodic table continues to evolve with the progress of science. In nature, only elements up to atomic number 94 exist; [a] to go further, it was necessary to synthesize new elements in the laboratory.

  3. Charge number - Wikipedia

    en.wikipedia.org/wiki/Charge_number

    The charge number in chemistry normally relates to an electric charge. This is a property of specific subatomic atoms. These elements define the electromagnetic contact between the two elements. A chemical charge can be found by using the periodic table. An element's placement on the periodic table indicates whether its chemical charge is ...

  4. Glossary of chemistry terms - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_chemistry_terms

    charge number A quantized value of electric charge calculated as the electric charge in coulombs divided by the elementary-charge constant, or z = q/e. Charge numbers for ions are denoted in superscript (e.g. Na + indicates a sodium ion with a charge number of positive one). Atomic numbers are charge numbers of atomic nuclei. Charles's law

  5. Pnictogen - Wikipedia

    en.wikipedia.org/wiki/Pnictogen

    Formation of multiple bonds is facilitated by their five valence electrons, as the octet rule permits a pnictogen to accept three electrons on covalent bonding. As 5 > 3, it leaves two unused electrons in a lone pair unless there is a positive charge around (like in [NH 4] +).

  6. Periodic trends - Wikipedia

    en.wikipedia.org/wiki/Periodic_trends

    Trend-wise, as one moves from left to right across a period in the modern periodic table, the electronegativity increases as the nuclear charge increases and the atomic size decreases. However, if one moves down in a group , the electronegativity decreases as atomic size increases due to the addition of a valence shell , thereby decreasing the ...

  7. Octet rule - Wikipedia

    en.wikipedia.org/wiki/Octet_rule

    The bonding in carbon dioxide (CO 2): all atoms are surrounded by 8 electrons, fulfilling the octet rule.. The octet rule is a chemical rule of thumb that reflects the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas.

  8. Chemical polarity - Wikipedia

    en.wikipedia.org/wiki/Chemical_polarity

    Two charges are present with a negative charge in the middle (red shade), and a positive charge at the ends (blue shade). In chemistry , polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment , with a negatively charged end and a positively charged end.

  9. Valence electron - Wikipedia

    en.wikipedia.org/wiki/Valence_electron

    The number of valence electrons of an element can be determined by the periodic table group (vertical column) in which the element is categorized. In groups 1–12, the group number matches the number of valence electrons; in groups 13–18, the units digit of the group number matches the number of valence electrons. (Helium is the sole ...