electron shell

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.