If it isMain family elements, then the number of families=the number of outermost electrons (except He)
The number of outermost electrons is less than (or equal to) 3, such asalkali metalAlkaline earth metal element, easy to lose the outermost electrons, reaching the stable structure of the outermost eight electrons, making it very strongMetallicityAndReducibility。But this pairSubfamily elementsNot applicable. For example, the outermost layer of gold and silver is one electron, and the outermost layer of mercury is two electrons, but both are very inactive.
The number of outermost electrons is more than (or equal to) 5, such ashalogen family, oxygen group elements, easy to get the stable structure of the outermost eight electrons, making it very strongNonmetallicAndOxidizability。
General status
When atomElectronic layerWhen the outermost electron is 4, such as the carbon group, it is easy to lose the outermost electron and get the electron, so it is easy to combine with other atomscovalent bondcompound.
When the outermost electron in the atomic electron layer is 8, such asNoble gas, has reached a stable structure, so it hardly combines with other elements.
Law of the number of outer electrons
Announce
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basic law
ExtranuclearNumber of electronic layersWhen n, thisElectronic layerNumber of electronsThe maximum number is 2n ^ 2, but the outermost layer of the whole atom does not exceed 8, the secondary layer does not exceed 18, and the penultimate layer does not exceed 32;
Element atoms with the same number of electrons in the outermost layer have more electron layers,Atomic radiusLarger;
The element with the outermost electron number equal to or greater than 3 (less than 8) must beMain family elements；
The element with more electrons in the outermost layer than in the second outer layer must be in the second period;
becauseEnergy level interleavingEnd>E (n+1) s.When ns and np are full (4 orbits in total, 8 electrons at most), the excess electrons are not filled with nd, but first form a new oneElectronic layer, fill in (n+1)S trackTherefore, the number of outermost electrons cannot exceed 8.
The same can explain why the secondary outer layerNumber of electronsNo more than 18.If the outermost layer is the nth layer, the second outer layer is the (n-1) layer.Because E (n-1) f>E (n+1) s>Enp, before the occurrence of the (n+1) layer, only (n-1) s, (n-1) p, and (n-1) d have electrons in the secondary outer layerSublayerThere are 9 orbits in total, which can accommodate up to 18 electrons, so the number of secondary outer electrons does not exceed 18.For example, the outermost layer of the atom is the fifth layer, and the secondary layer is the fourth layer. Because E4f>E6s>E5p, before the sixth layer appears, the secondary layer (the fourth layer) only has electrons on the 4s, 4p, and 4d orbits. These three sub layers have a total of 9 orbits, which can accommodate up to 18 electrons, that is, the secondary layer does not exceed 18 electrons.
