Electron Configuration and Orbital Diagram.pptx

electron configuration

1. Electron Configuration and Orbital Diagram

2. Each electron in an atom has a unique set of quantum numbers. How these electrons are distributed among the orbitals in an atom is given by the electron configuration. In writing electron configurations, nich orbital and the electron(s) it holds are represented

3. Take note that in a neutral atom, the number of electrons is equal to the number of protons. Thus, the number of electrons in an atom is equal to its atomic number

4. The Aufbau principle (also known as the building up principle ) of filling up of orbitals states that electrons must first occupy the orbitals with lower energies than those with higher energies. The first two orbitals (1s and 2s) are each occupied first with two electrons.

5. The sequence of filling the orbitals is depicted in figure 6-15. As the figure shows, the first orbital that is assigned two electrons (of opposite spins) is the 1s orbital, followed by two electrons for 2s, and another two for each 2p orbital (a total of six electrons for P x , P y , and P z ). This sequence goes on until all the electrons in an atom have been assigned to orbitals. Note that the maximum number of electrons for the s orbital is two , six for p, 10 for d, and 14 for f.

6. Hund’s Rule of Maximum Multiplicity , which states that for degenerate orbitals (orbitals with similar energies such as the three p orbitals), the electrons will singly occupy each orbital and with parallel spins before they pair up. The same is true for the d and f orbitals. This pairing up rule gives the atom the most stable distribution of its electrons, just like how the Aufbau principle predicts the tendency of an atom to acquire its most stable electron configuration (with minimum repulsion).

7. The outermost energy level of an atom is called its valence shell , and the electrons occupying these shells are called valence electrons . The inner shells that are completely filled are called closed shells . Lithium has only one valence electron, while oxygen has six. Notice that the valence shell of the noble gas neon is completely filled, and is thus very stable as the shell of the other noble gases.

8. Heavier atoms that have more electrons will have very long electron configurations. In this case, a noble gas with a similar closed-shell configuration to the atom of interest is used as a shortcut and is referred to as a core symbol written inside brackets. The resulting configuration is called noble gas electron configuration . The two possible configurations for lead are given below. Pb (A=82) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 2 Electron configuration of Xe [Xe] 6s 2 4f 14 5d 10 6p 2

9. Transition metals with d 4 and d 9 configurations tend to adopt a more stabilized half-filled or fully filled configuration by using one electron from the nearby s orbital. For example, the electron configuration for chromium is [ Ar ] 4s 1 3d 5 instead of 4s²3d 4 ; that of copper is [ Ar ] 4s 1 3d 10 instead of 4s²3d 9 .

10. Paramagnetism and Diamagnetism Paramagnetism and diamagnetism are properties of elements explained by electron distribution. Paramagnetism refers to the characteristic of an element to be slightly attracted to a magnet. It results from the presence of unpaired electrons in some of the atomic orbitals of an atom, which creates a net magnetic moment for the atom.

11. These electrons tend to align themselves in the direction of an external magnetic field. Arsenic (A=33), which has three unpaired electrons in its 4p orbitals, is considered paramagnetic.

12. Elements without unpaired electrons in their orbitals exhibit diamagnetism. Diamagnetism is characterized by non-attraction, or even a slight repulsion, of an element to a magnet. When the electrons in an atom's orbitals are all paired, the atom does not have a net magnetic moment and is not attracted by an external magnetic field. Krypton (A=36), which has fully filled 4p orbitals, is diamagnetic.

13. When paramagnetic species or atoms are close to each other (as in a metal rod or wire), their individual magnetic moments could interact with each other and spontaneously align. Such is the case for a few metals such as iron, cobalt, and nickel which are said to exhibit ferromagnetism . Ferromagnetism is a phenomenon that greatly enhances the paramagnetism of a material in such a way that it becomes permanently attracted to a magnet.