Aufbau principle atomic configuration

Aufbau principle In building up the electronic configuration of an atom or a molecule in its ground state, the electrons are placed in the orbitals in order of increasing energy. 

To arrive at the electronic configuration of an atom the appropriate number of electrons are placed in the orbitals in order of energy, the orbitals of lower energy being filled first (Aufbau principle ), subject to the proviso that for a set of equivalent orbitals - say the three p orbitals in a set - the electrons are placed one... 

MOs around them - rather as we construct atomic orbitals (AOs) around a single bare nucleus. Electrons are then fed into the MOs in pairs (with the electron spin quantum number = 5) in order of increasing energy using the aufbau principle, just as for atoms (Section 7.1.1), to give the ground configuration of the molecule. 

Aufbau principle (Section 1.3) The rules for determining the electron configuration of an atom. 

A neutral helium atom has two electrons. To write the ground-state electron configuration of He, we apply the aufbau principle. One unique set of quantum numbers is assigned to each electron, moving from the most stable orbital upward until all electrons have been assigned. The most stable orbital is always ly( = l,/ = 0, JW/ = 0 ). 

Use the aufbau principle to write complete electron configurations and complete orbital diagrams for atoms of the following elements sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, and argon (atomic numbers 11 through 18). 

Use the aufbau principle to write complete electron configurations for the atom of the element that fits the following descriptions. 

For each of the elements below, use the aufbau principle to write the full and condensed electron configurations and draw partial orbital diagrams for the valence electrons of their atoms. You may consult the periodic table in Appendix C, or any other periodic table that omits electron configurations. 

Watch the video clips at www.brightredbooks. net. These will help you understand how to use the Pauli exclusion principle, the aufbau principle and Hund s rule to write electronic configurations of atoms. 

The ground-state electron configuration of a multielectron atom is arrived at by following a series of rules called the aufbau principle. 

Aufbau principle The procedure used to find the ground-state electron configuration of an atom or ion. 

This model takes a more fundamental approach by regarding a molecule as a collection of valence electrons and positive cores. Just as the nature of atomic orbitals derives from the spherical symmetry of the atom, so will the properties of these new molecular orbitals be controlled by the interaction of the valence electrons with the multiple positive centers of these atomic cores. These new orbitals, unlike those of the hybrid model, are delocalized that is, they do not belong to any one atom but extend over the entire region of space that encompasses the bonded atoms. The available (valence) electrons then fill these orbitals from the lowest to the highest, very much as in the Aufbau principle that you learned for working out atomic electron configurations. For small mole-... 

Knowing these three rules—the Aufbau principle, the Pauli exclusion principle, and Hund s rule—and the energy levels of the orbitals shown in Figure 2.4, it is possible to predict the electron configurations of most atoms. And these configurations are one of the keys needed to unlock the secrets of the chemical bond. 

So how is an electron configuration written First, the number of total electrons must be determined. This is the equal to the mass number for neutral atoms. For ions, the total electron is corrected for the charge (add electrons for anions subtract electrons for cations). The electrons are added according to Hund s rule and the Aufbau principle. Figure 10.3 describes the order in which the electrons are added. Keep in mind the maximum number of electrons in each type of orbital s orbitals hold two electrons, p orbitals hold six electrons, d orbitals hold ten electrons, and f orbitals hold 14 electrons. 

For a model to be used effectively, we must understand its strengths and weaknesses and ask only appropriate questions. An illustration of this point is the simple aufbau principle used to explain the electron configurations of the elements. Although this model correctly predicts the configuration for most atoms, chromium and copper do not agree with the predictions. Detailed studies show that the configurations of chromium and copper result from complex electron interactions that are not taken into account in the simple model. However, this does not mean that we should discard the simple model that is so useful for most atoms. Instead, we must apply it with caution and not expect it to be correct in every case. 

Aufbau principles, 126, 130 ground-state electron configurations and notations, 126-129 history of development, 123-124 Pauli exclusion principle, 123 periodicity of atomic properties, 131-132... 

Write the electron configuration of an atom by using the Pauli exclusion principle and the aufbau principle. 

The Pauli exclusion principle is one rule to help you write an electron configuration for an atom. Another rule is the aufbau principle. Aufbau is the German word for building up. The aufbau principle states that electrons fill orbitals that have the lowest energy first. 

These experimental results for neon are consistent with the electron configuration Ne ls 2s 2p predicted by the aufbau principle. Ionization energies measured in this way are used to construct the energy-level diagram for atoms and to show explicitly the value of the ground-state energy. 

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