electron

Examples of electron in the following topics:

• The Shielding Effect and Effective Nuclear Charge

  • Therefore, these electrons are not as strongly bound as electrons closer to the nucleus.
  • 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.

• Electronic Effects

  • Such charges are produced by removing (or adding) electrons from (or to) an object.
  • Electron deficient species, which may or may not be positively charged, are attracted to electron rich species, which may or may not be negatively charged.
  • Electrophiles: Electron deficient atoms, molecules or ions that seek electron rich reaction partners.
  • Nucleophiles: Electron rich atoms, molecules or ions that seek electron deficient reaction partners.

• General Rules for Assigning Electrons to Atomic Orbitals

  • An atom's electrons exist in discrete atomic orbitals, and the atom's electron configuration can be determined using a set of guidelines.
  • This nucleus is surrounded by electrons.
  • An atom's electron shell can accommodate 2n2 electrons, where n is the energy level.
  • An element's electron configuration is the arrangement of the electrons in the shells.
  • Electrons that occur together in an orbital are called an electron pair.

• Electron Configurations

  • The electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals.
  • The electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals.
  • Electron configurations describe electrons as each moving independently in an orbital, in an average field created by all other orbitals.
  • For atoms or molecules with more than one electron, the motion of electrons are correlated and such picture is no longer exact.
  • However, the electronic wave function is usually dominated by a very small number of configurations and therefore the notion of electronic configuration remains essential for multi-electron systems.

• Multielectron Atoms

  • However, when more electrons are involved, each electron (in the $n$-shell) feels not only the electromagnetic attraction from the positive nucleus, but also repulsion forces from other electrons in shells from '1' to '$n$'.
  • This causes the net force on electrons in the outer electron shells to be significantly smaller in magnitude.
  • Therefore, these electrons are not as strongly bonded to the nucleus as electrons closer to the nucleus.
  • Each has 10 electrons, and the number of nonvalence electrons is two (10 total electrons minus eight valence electrons), but the effective nuclear charge varies because each has a different number of protons:
  • A multielectron atom with inner electrons shielding outside electrons from the positively charged nucleus

• The Building-Up (Aufbau) Principle

  • The Aufbau principle determines an atom's electron configuration by adding electrons to atomic orbitals following a defined set of rules.
  • As electrons are added, they assume the most stable shells with respect to the nucleus and the electrons already present.
  • When there are two electrons in an orbital, the electrons are called an electron pair.
  • If the orbital only has one electron, this electron is called an unpaired electron.
  • Put one electron in each of the three p orbitals in the second energy level (the 2p orbitals) and then if there are still electrons remaining, go back and place a second electron in each of the 2p orbitals to complete the electron pairs.

• Ions and Ionic Bonds

  • This movement of electrons from one element to another is referred to as electron transfer.
  • As illustrated, sodium (Na) only has one electron in its outer electron shell.
  • When sodium loses an electron, it will have 11 protons, 11 neutrons, and only 10 electrons.
  • Therefore, it tends to gain an electron to create an ion with 17 protons, 17 neutrons, and 18 electrons.
  • In the formation of an ionic compound, metals lose electrons and nonmetals gain electrons to achieve an octet.

• Electron Microscopy

  • Electron microscopy uses magnetic coils to direct a beam of electrons from a tungsten filament through a specimen and onto a monitor.
  • Electron microscopy uses a beam of electrons as an energy source.
  • Magnets are used to focus the electrons on the object viewed.
  • There are two types of electron microscopes .
  • The more traditional form is the transmission electron microscope (TEM).

• Electron Affinity

  • The electron affinity (Eea) of a neutral atom or molecule is defined as the amount of energy released when an electron is added to it to form a negative ion, as demonstrated by the following equation:
  • Mulliken used a list of electron affinities to develop an electronegativity scale for atoms by finding the average of the electron affinity and ionization potential.
  • A molecule or atom that has a more positive electron affinity value is often called an electron acceptor; one with a less positive electron affinity is called an electron donor.
  • To use electron affinities properly, it is essential to keep track of the sign.
  • Electron affinity follows the trend of electronegativity: fluorine (F) has a higher electron affinity than oxygen (O), and so on.

• 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.
  • An atom may gain or lose electrons to achieve a full valence shell, the most stable electron configuration.