core electrons

Examples of core electrons in the following topics:

• The Shielding Effect and Effective Nuclear Charge

  • The attraction between this lone valence electron and the nucleus with 11 protons is shielded by the other 10 core electrons.
  • Ne has 10 electrons.
  • Thus the number of nonvalence electrons is 2 (10 total electrons - 8 valence).
  • Flourine has 9 electrons but F- has gained an electron and thus has 10.
  • Sodium has 11 electrons but the Na+ ion has lost an electron and thus has 10.

• Electromagnetic Spectrum

  • Photon energy is directly proportional to the wave frequency, so gamma ray photons have the highest energy (around a billion electron volts), while radio wave photons have very low energy (around a femto-electron volt).
  • An example would be the oscillation of the electrons in an antenna.
  • Ultraviolet: Excitation of molecular and atomic valence electrons, including ejection of the electrons (photoelectric effect).
  • X-rays: Excitation and ejection of core atomic electrons, Compton scattering (for low atomic numbers).
  • Gamma rays: Energetic ejection of core electrons in heavy elements, Compton scattering (for all atomic numbers), excitation of atomic nuclei, including dissociation of nuclei.

• Electron Transport Chain

  • The electron transport chain uses the electrons from electron carriers to create a chemical gradient that can be used to power oxidative phosphorylation.
  • The Q molecule is lipid soluble and freely moves through the hydrophobic core of the membrane.
  • Once it is reduced to QH2, ubiquinone delivers its electrons to the next complex in the electron transport chain.
  • As a result, the iron ion at its core is reduced and oxidized as it passes the electrons, fluctuating between different oxidation states: Fe2+ (reduced) and Fe3+ (oxidized).
  • The electron transport chain is a series of electron transporters embedded in the inner mitochondrial membrane that shuttles electrons from NADH and FADH2 to molecular oxygen.

• Electron Configurations of Atoms

  • Electron shell #1 has the lowest energy and its s-orbital is the first to be filled.
  • In the third period of the table, the atoms all have a neon-like core of 10 electrons, and shell #3 is occupied progressively with eight electrons, starting with the 3s-orbital.
  • The highest occupied electron shell is called the valence shell, and the electrons occupying this shell are called valence electrons.
  • The chemical properties of the elements reflect their electron configurations.
  • These atoms have only one electron in the valence shell, and on losing this electron arrive at the lower shell valence octet.

• Electronegativity and Oxidation Number

  • Electronegativity is a property that describes the tendency of an atom to attract electrons (or electron density) toward itself.
  • The higher its electronegativity, the more an element attracts electrons.
  • Properties of a free atom include ionization energy and electron affinity.
  • Where electrons are in space is a contributing factor because the more electrons an atom has, the farther from the nucleus the valence electrons will be, and as a result they will experience less positive charge; this is due to their increased distance from the nucleus, and because the other electrons in the lower-energy core orbitals will act to shield the valence electrons from the positively charged nucleus.
  • One way to characterize atoms in a molecule and keep track of electrons is by assigning oxidation numbers.

• Virus Classification

  • The surface structure of virions can be observed by both scanning and transmission electron microscopy, whereas the internal structures of the virus can only be observed in images from a transmission electron microscope.
  • The virus core contains the genome or total genetic content of the virus.
  • Viruses are classified based on their core genetic material and capsid design.
  • (a) Rabies virus has a single-stranded RNA (ssRNA) core and an enveloped helical capsid, whereas (b) variola virus, the causative agent of smallpox, has a double-stranded DNA (dsDNA) core and a complex capsid.
  • Transmission electron micrographs of various viruses show their structures.

• Reactions of Aromatic Compounds

  • The electrons in the pi system of the benzene ring are responsible for the reactivity observed.
  • While aromatic compounds are best represented by a continuous electron density evenly distributed around the aromatic core, the alternating single and double bonds that are commonly drawn are very useful when predicting the reactivity of aromatic compounds.
  • The presence of an electron-withdrawing group on the ring can speed up the progress of this class of reactions.
  • It states that an electron-donating substituent generally accelerates substitution and directs reactivity toward the positions that are ortho and para to it on the ring, while an electron-withdrawing substituent will slow reaction progress and favor the meta position on the ring.
  • Due to the electrons provided by the NH2 group, this intermediate is stabilized, and the para-substitution is favored.

• Coloring Agents

  • Many of the properties of metal complexes are dictated by their electronic structures.
  • This approach is the essence of crystal field theory (CFT), which is a core concept in inorganic chemistry.
  • However, the electron remains centered on the metal.
  • The overall charge of the system remains the same, but the localization of the electron changes.
  • These phenomena can be observed with the aid of electronic spectroscopy (also known as UV-Vis).

• Solenoids, Current Loops, and Electromagnets

  • Solenoids are loops of wire around a metallic core, and can be used to create controlled magnetic fields.
  • In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core; it produces a magnetic field when an electric current is passed through it.
  • Ferromagnetism, for example, results from an internal cooperative alignment of electron spins, possible in some materials but not in others.

• Global Inequality

  • In contrast, in the modern world, the rise of capitalism brought modern attitudes, modern technologies such as machinery and electronics, and modern institutions which helped countries progress and have a higher standard of living.
  • The world economy is a system divided into a hierarchy of three types of countries: core, semiperipheral, and peripheral.
  • Core countries own most of the world's capital and technology and have great control over world trade and economic agreements.
  • Semiperipheral countries generally provide labor and materials to core countries.
  • Core countries extract raw materials with little cost.