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  2. Periodic trends - Wikipedia

    en.wikipedia.org/wiki/Periodic_trends

    It is due to the fact that the atomic size increases as we move down the group, but at the same time the effective nuclear charge increases due to poor shielding of the inner d and f electrons. As a result, the force of attraction of the nucleus for the electrons increases and hence the electronegativity increases from aluminium to thallium ...

  3. Electronegativity - Wikipedia

    en.wikipedia.org/wiki/Electronegativity

    The anomalously high electronegativity of lead, in particular when compared to thallium and bismuth, is an artifact of electronegativity varying with oxidation state: its electronegativity conforms better to trends if it is quoted for the +2 state with a Pauling value of 1.87 instead of the +4 state.

  4. Evolution of biological complexity - Wikipedia

    en.wikipedia.org/wiki/Evolution_of_biological...

    Passive versus active trends in complexity. Organisms at the beginning are red. Numbers are shown by height with time moving up in a series. If evolution possessed an active trend toward complexity (orthogenesis), as was widely believed in the 19th century, [12] then we would expect to see an active trend of increase over time in the most common value of complexity among organisms.

  5. Electronegativities of the elements (data page) - Wikipedia

    en.wikipedia.org/wiki/Electronegativities_of_the...

    Electronegativity is not a uniquely defined property and may depend on the definition. The suggested values are all taken from WebElements as a consistent set. Many of the highly radioactive elements have values that must be predictions or extrapolations, but are unfortunately not marked as such.

  6. Extended periodic table - Wikipedia

    en.wikipedia.org/wiki/Extended_periodic_table

    This is an accepted version of this page This is the latest accepted revision, reviewed on 27 January 2025. Periodic table of the elements with eight or more periods Extended periodic table Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium ...

  7. Chemical bond - Wikipedia

    en.wikipedia.org/wiki/Chemical_bond

    Ionic bonding is a type of electrostatic interaction between atoms that have a large electronegativity difference. There is no precise value that distinguishes ionic from covalent bonding, but an electronegativity difference of over 1.7 is likely to be ionic while a difference of less than 1.7 is likely to be covalent. [21]

  8. Period 2 element - Wikipedia

    en.wikipedia.org/wiki/Period_2_element

    A period 2 element is one of the chemical elements in the second row (or period) of the periodic table of the chemical elements.The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases; a new row is started when chemical behavior begins to repeat, creating columns of elements with similar properties.

  9. Hydrogen bond - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_bond

    The most frequent donor and acceptor atoms are nitrogen (N), oxygen (O), and fluorine (F), due to their high electronegativity and ability to engage in stronger hydrogen bonding. The term "hydrogen bond" is generally used for well-defined, localized interactions with significant charge transfer and orbital overlap, such as those in DNA base ...