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THE PERIODIC TABLE. In the modern periodic table , you find the elements placed in vertical columns , called groups , and horizontal lines , called periods . THE PERIODS. The elements are placed in horizontal lines , on crescent atomic number .
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THE PERIODIC TABLE In the modernperiodictable, youfind the elementsplaced in verticalcolumns, calledgroups, and horizontallines, calledperiods.
THE PERIODS The elements are placed in horizontallines, on crescentatomicnumber. Eachlineiscalledperiod. There are 7 periods. Eachperiodstartswithanelementwithonlyone electron in a newprincipallevelofenergy.
THE FIRST PERIOD Itcontainsonly 2 elements, H and Hebecause at the mostthere are 2 electrons in the first level.
THE SECOND PERIOD Itcontains 8 elements, fromLi to Ne, because at the mostthere are 8 electrons in the secondlevel.
THE THIRD PERIOD The thirdperiodshouldcontain 18 elements, but the sublevel 3dfollows the 4s in the energeticdiagram, so in the thirdperiodwehaveonly 8 elementscorrespondingtofillingofsublevels 3s and 3p.
THE FOURTH PERIOD The fourthperiodiscomposedby 18 elementsfromKtoKr. Thisperiodcontains 10 elements, fromSctoZn, correspondingtofillingofsublevel 3d.
THE FIFTH PERIOD The fifthperiodiscomposedby 18 elementsfromRbtoXe. They complete the dsublevel.
THE SIXTH PERIOD The sixthperiodiscomposedby 18 elementsfromCs toRn. Theyfill the f sublevel. In thisperiodthere are otherfourteenelementscalled “Lantanidi”. Theyhave the same electronic configurationofLa.
THE SEVENTH PERIODThe seventhperiodiscomposedby 3 elementsfromFrtoAc. They complete the fsublevel. In thisperiodthere are otherfourteenelementscalled “Attinidi”. Theyhave the same electronic configurationofAc. The elementsfromUtoLrare artificial and theirnames derive from the onesoftheirdiscoverers.