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  2. 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 ...

  3. VSEPR theory - Wikipedia

    en.wikipedia.org/wiki/VSEPR_theory

    The steric number of a central atom in a molecule is the number of atoms bonded to that central atom, called its coordination number, plus the number of lone pairs of valence electrons on the central atom. [11] In the molecule SF 4, for example, the central sulfur atom has four ligands; the coordination number of sulfur is four. In addition to ...

  4. Electronegativity - Wikipedia

    en.wikipedia.org/wiki/Electronegativity

    Electronegativity, symbolized as χ, is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. [1] An atom's electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the ...

  5. Bent's rule - Wikipedia

    en.wikipedia.org/wiki/Bent's_rule

    The same logic can be applied to ammonia (107.0° HNH bond angle, with three N(~sp 3.4 or 23% s) bonding orbitals and one N(~sp 2.1 or 32% s) lone pair), the other canonical example of this phenomenon. The same trend holds for nitrogen containing compounds.

  6. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    Each distinct atomic number therefore corresponds to a class of atom: these classes are called the chemical elements. [5] The chemical elements are what the periodic table classifies and organizes. Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on.

  7. Ionization energy - Wikipedia

    en.wikipedia.org/wiki/Ionization_energy

    Group 14: Lead's unusually high ionization energy ( 82 Pb: 7.42 eV) is, akin to that of group 13's thallium, a result of the full 5d and 4f subshells. The lanthanide contraction and the inefficient screening of the nucleus by the 4f electrons results in slightly higher ionization energy for lead than for tin ( 50 Sn: 7.34 eV). [38] [5]

  8. 15 holiday gifts for dementia patients and caregivers ...

    www.aol.com/15-holiday-gifts-dementia-patients...

    11. A memory phone can store photos with names and contact information. 12. Puzzles and activity books stimulate the brain and promote cognitive sharpness.. 13. Card games and board games ...

  9. 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.