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Stable isotopesradioactive isotopes

orbitals

ssss1 Distribution of electrons in the principal quantum levels (“electron shells”) of uranium: K‐shell electrons violet; L‐shell blue; M‐shell bluish green; N‐shell green; O‐shell yellow; P‐shell orange and Q‐shell red.

Every electron in an atom possesses a unique set of properties that distinguishes it from all the other electrons in that atom. An individual electron's identity is given by four properties that include its (1) principal quantum number, (2) azimuthal quantum number, (3) magnetic quantum number, and (4) spin number. Each electron in the electron cloud possesses a unique combination of the four quantum properties.

principal quantum number (n)principal quantum energy region,levelshell1, 2, 3, 4, 5, 6 or 7K, L, M, N, O, P or Q

azimuthal or angular momentum quantum numberssubshells, p, d, and fmagnetic quantum number (m)spin number (±½)

Atomic nuclei were created largely during the “big bang,” by subsequent fusion reactions between protons and neutrons in the interior of stars, and in supernova. When elements are formed, electrons are added to the lowest available quantum level in numbers equal to the number of protons in the nucleus. Electrons are added to the atoms in a distinct sequence, from lowest quantum level electrons to highest quantum level electrons. The relative quantum energy of each electron is shown in ssss1.