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stabilirea grupei si perioadei primelor 20 de elemente chimice

Răspuns :

H gr1per1a,He gr8per8a,Li gr2per1a,Be gr2per2a,B gr2per3a, C gr2per4a, N gr2per5a,O gr2 per6a,Fgr2per7a, Ne gr2 per8a,Na gr3per1a, Mg gr3per2a,Al gr3per3a, Si gr3per4a, P gr3per5a,,S gr3per6a, Cl gr3per7a, Ar gr3per8a,K gr4per1a,Ca gr4 per2a