3.4 Electronic Structure of Atoms (Electron Configurations) - Chemistry_ Atoms First 2e _ OpenStax.p

This preview shows page 1 - 3 out of 12 pages.

5/23/20203.4 Electronic Structure of Atoms (Electron Configurations) - Chemistry: Atoms First 2e | OpenStax1/12By the end of this section, you will be able to:Derive the predicted ground-state electron configurations of atomsIdentify and explain exceptions to predicted electron configurations for atoms and ionsRelate electron configurations to element classifications in the periodic tableHaving introduced the basics of atomic structure and quantum mechanics, we can use our understandingof quantum numbers to determine how atomic orbitals relate to one another. This allows us to determinewhich orbitals are occupied by electrons in each atom. The specific arrangement of electrons in orbitals ofan atom determines many of the chemical properties of that atom.Orbital Energies and Atomic StructureThe energy of atomic orbitals increases as the principal quantum number,n, increases. In any atom with twoor more electrons, the repulsion between the electrons makes energies of subshells with different values ofldiffer so that the energy of the orbitals increases within a shell in the orders<p<d<f.Figure 3.24depictshow these two trends in increasing energy relate. The 1sorbital at the bottom of the diagram is the orbitalwith electrons of lowest energy. The energy increases as we move up to the 2sand then 2p, 3s, and 3porbitals, showing that the increasingnvalue has more influence on energy than the increasinglvalue forsmall atoms. However, this pattern does not hold for larger atoms. The 3dorbital is higher in energy than the4sorbital. Such overlaps continue to occur frequently as we move up the chart.Figure 3.24Generalized energy-level diagram for atomic orbitals in an atom with two or more electrons (not to scale).Electrons in successive atoms on the periodic table tend to fill low-energy orbitals first. Thus, many studentsfind it confusing that, for example, the 5porbitals fill immediately after the 4d, and immediately before the6s. The filling order is based on observed experimental results, and has been confirmed by theoreticalcalculations. As the principal quantum number,n, increases, the size of the orbital increases and theelectrons spend more time farther from the nucleus. Thus, the attraction to the nucleus is weaker and theenergy associated with the orbital is higher (less stabilized). But this is not the only effect we have to takeinto account. Within each shell, as the value oflincreases, the electrons are less penetrating (meaning thereis less electron density found close to the nucleus), in the orders>p>d>f. Electrons that are closer to the
5/23/20203.4 Electronic Structure of Atoms (Electron Configurations) - Chemistry: Atoms First 2e | OpenStax2/12

Upload your study docs or become a

Course Hero member to access this document

Upload your study docs or become a

Course Hero member to access this document

End of preview. Want to read all 12 pages?

Upload your study docs or become a

Course Hero member to access this document

Term
Fall
Professor
Frank Merante
Tags
Atom, Periodic Table, Atomic orbital, Electron shell, electron configurations

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture