electron shell

(noun)

The collective states of all electrons in an atom having the same principal quantum number (visualized as an orbit in which the electrons move).

Related Terms

  • orbital
  • octet rule

Examples of electron shell in the following topics:

  • Electron Shells and the Bohr Model

    • These orbits form electron shells or energy levels, which are a way of visualizing the number of electrons in the various shells.
    • Electrons fill orbit shells in a consistent order.
    • The innermost shell has a maximum of two electrons, but the next two electron shells can each have a maximum of eight electrons.
    • As shown, helium has a complete outer electron shell, with two electrons filling its first and only shell.
    • In this model, electrons exist within principal shells.
  • Electron Orbitals

    • The second electron shell may contain eight electrons.
    • Lithium (Li) contains three electrons that occupy the first and second shells.
    • Larger elements have additional orbitals, making up the third electron shell.
    • Principal shell 3n has s, p, and d subshells and can hold 18 electrons.
    • Principal shell 4n has s, p, d, and f orbitals and can hold 32 electrons.
  • Ions and Ionic Bonds

    • This results in a full outermost electron shell and makes them energetically more stable.
    • As illustrated, sodium (Na) only has one electron in its outer electron shell.
    • It takes less energy for sodium to donate that one electron than it does to accept seven more electrons to fill the outer shell .
    • In this example, sodium will donate its one electron to empty its shell, and chlorine will accept that electron to fill its shell.
    • In this example, sodium loses one electron to empty its shell and chlorine accepts that electron to fill its shell.
  • The Chemical Basis for Life

    • Individual carbon atoms have an incomplete outermost electron shell.
    • With an atomic number of 6 (six electrons and six protons), the first two electrons fill the inner shell, leaving four in the second shell.
    • Each of its four hydrogen atoms forms a single covalent bond with the carbon atom by sharing a pair of electrons.
    • This results in a filled outermost shell.
  • Covalent Bonds and Other Bonds and Interactions

    • The electron from the hydrogen splits its time between the incomplete outer shell of the hydrogen atom and the incomplete outer shell of the oxygen atom.
    • In return, the oxygen atom shares one of its electrons with the hydrogen atom, creating a two-electron single covalent bond.
    • To completely fill the outer shell of oxygen, which has six electrons in its outer shell, two electrons (one from each hydrogen atom) are needed.
    • Each hydrogen atom needs only a single electron to fill its outer shell, hence the well-known formula H2O.
    • The electrons that are shared between the two elements fill the outer shell of each, making both elements more stable.
  • Chemical Reactions and Molecules

    • According to the octet rule, elements are most stable when their outermost shell is filled with electrons.
    • However, since not all elements have enough electrons to fill their outermost shells, atoms form chemical bonds with other atoms, which helps them obtain the electrons they need to attain a stable electron configuration.
    • Atoms can form molecules by donating, accepting, or sharing electrons to fill their outer shells.
    • When two hydrogens and an oxygen share electrons via covalent bonds, a water molecule is formed.
  • Rhizaria

    • As a group, the forams exhibit porous shells, called tests, that are built from various organic materials and typically hardened with calcium carbonate.
    • The shells of dead radiolarians sink to the ocean floor, where they may accumulate in 100 meter-thick depths.
    • This fossilized radiolarian shell was imaged using a scanning electron microscope.
  • Classification of Phylum Mollusca

    • Gastropoda includes shell-bearing species as well as species with a reduced shell.
    • These animals are asymmetrical and usually present a coiled shell.
    • Cephalopods are a class of shell-bearing animals as well as mollusks with a reduced shell.
    • These animals bear a single conical shell, which has both ends open .
    • The empty shell of the giant clam, Tridacna gigas.
  • Characteristics of Amniotes

    • The distinguishing characteristic of amniotes, a shelled egg with an amniotic membrane, allowed them to venture onto land.
    • This was a significant development that distinguished them from amphibians, which were restricted to moist environments due their shell-less eggs.
    • Although the shells of various amniotic species vary significantly, they all allow retention of water.
    • The shells of bird eggs are composed of calcium carbonate and are hard, but fragile.
    • The shells of reptile eggs are leathery and require a moist environment.
  • Electrons and Energy

    • In living systems, a small class of molecules functions as electron shuttles: they bind and carry high-energy electrons between compounds in cellular pathways.
    • These compounds can be easily reduced (that is, they accept electrons) or oxidized (they lose electrons).
    • It is noteworthy that NAD+must accept two electrons at once; it cannot serve as a one-electron carrier .
    • When electrons are added to a compound, the compound is reduced.
    • When electrons are removed from a compound, the compound is oxidized.
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