Atoms and atomic theory
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3.2 Reading: Rules of assigning electrons to orbitals 1. Electrons occupy orbitals in a way that …(1)…. Electrons occupy the subshells in the principal electronic shells; first the 1s, then 2s, 2p, and so on. The exact order of filling of orbitals has been established by experiment, principally through spectroscopy and magnetic studies, and it is this order based on experiment that we must follow in assigning electron configurations to the elements. With only a few exceptions, the order in which orbitals fill is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p Some students find the diagram pictured in Figure 1 a useful way to remember this order, but the best method of establishing the order of … (2)…. 2. No two electrons in an atom can have all four quantum numbers alike the Pauli exclusion principle. In 1926, Wolfgang Pauli explained complex features of emission spectra associated with atoms in magnetic fields by proposing that no two electrons in an atom can have all four quantum numbers alike. The first three quantum numbers, n, l and m l , determine a specific Figure 1. The order of filling of electronic subshells English in chemistry 1 – 2017 TS. Nguyễn Tuyết Phương – TS. Trần Thu Phương 9 orbital. Two electrons may have these three quantum numbers alike; but if they do, …(3)…, the spin quantum number. Another way to state this result is that only two electrons may occupy the same orbital, and these electrons must have opposing spins. Because of this limit of two electrons per orbital, the capacity of a subshell for electrons can be obtained by doubling the number of orbitals in the subshell. Thus, …(4)…; the p subshell consists of three orbitals with a total capacity of six electrons; and so on. tải về 0.52 Mb. Chia sẻ với bạn bè của bạn:
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