![]() The designations A and B have been extensively and rather arbitrarily used in the meantime in textbooks and in publications. This version of the periodic table was distributed for many years by the Sargent-Welch Scientific Company, Skokie, Illinois, USA. The group was later switched to the right side and usually labeled as Group VlllA. The Noble Gas Group was originally attached by Ueming to the left side of the periodic table. The iron, cobalt, and nickel groups were designated neither A nor B. The numeration was chosen so that the characteristic oxides of the B groups would correspond to those of the A groups. Deming used the long periodic table in his textbook General Chemistry (See following diagram with Roman numerals only Ref.2), which appeared in the USA for the first time in 1923, and designated the first two and the last five Main Groups with the notation "A", and the intervening Transition Groups with the notation "B". The IUPAC recommended Periodic Table is given below (ignore the Roman numerals, which I put in there to explain):Īccording to Ref.1, the confusion of Periodic Table of Elements has been addressed as follows: I believe I-VIII Roman numeral nomenclature belong to CAS system while 1-18 Arabic numeral groups are recommended by IUPAC (Ref.1). Even though your question get downvoted, I think it is an legitimate question for people to understand the trend.
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