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  2. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules or crystals. The ability of atoms to attach and detach from each other is responsible for most of the physical changes observed in nature. Chemistry is the science that studies these changes.

  3. Molecular self-assembly - Wikipedia

    en.wikipedia.org/wiki/Molecular_self-assembly

    Molecular self-assembly is a key concept in supramolecular chemistry. [6] [7] [8] This is because assembly of molecules in such systems is directed through non-covalent interactions (e.g., hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, pi-stacking interactions, and/or electrostatic) as well as electromagnetic interactions.

  4. Periodic trends - Wikipedia

    en.wikipedia.org/wiki/Periodic_trends

    The atomic radius is half of the distance between two nuclei of two atoms. The atomic radius is the distance from the atomic nucleus to the outermost electron orbital in an atom. In general, the atomic radius decreases as we move from left-to-right in a period, and it increases when we go down a group.

  5. Aufbau principle - Wikipedia

    en.wikipedia.org/wiki/Aufbau_principle

    In atomic physics and quantum chemistry, the Aufbau principle (/ ˈ aʊ f b aʊ /, from German: Aufbauprinzip, lit. 'building-up principle'), also called the Aufbau rule, states that in the ground state of an atom or ion, electrons first fill subshells of the lowest available energy, then fill subshells of higher energy. For example, the 1s ...

  6. Electron shell - Wikipedia

    en.wikipedia.org/wiki/Electron_shell

    In chemistry and atomic physics, an electron shell may be thought of as an orbit that electrons follow around an atom's nucleus.The closest shell to the nucleus is called the "1 shell" (also called the "K shell"), followed by the "2 shell" (or "L shell"), then the "3 shell" (or "M shell"), and so on further and further from the nucleus.

  7. Covalent bond - Wikipedia

    en.wikipedia.org/wiki/Covalent_bond

    A double bond between two given atoms consists of one σ and one π bond, and a triple bond is one σ and two π bonds. [8] Covalent bonds are also affected by the electronegativity of the connected atoms which determines the chemical polarity of the bond. Two atoms with equal electronegativity will make nonpolar covalent bonds such as H–H.

  8. NFL Week 15 bold predictions: Which players and teams will ...

    www.aol.com/nfl-week-15-bold-predictions...

    By the time they’re all over, we are going to call it the most fun few hours of the entire season. — Chris Bumbaca. Saquon Barkley will surpass 2,000 yards from scrimmage in Week 15.

  9. Chemical element - Wikipedia

    en.wikipedia.org/wiki/Chemical_element

    In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the same atomic number, or number of protons. Nuclear scientists, however, define a pure element as one that consists of only one isotope. [18] For example, a copper wire is 99.99% chemically pure if 99.99% of its atoms are copper, with 29 protons each.