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...Class x chemistry chapter periodic classification of elements the table is a tabular method displaying in such way that having similar properties occur same vertical column or group without it would be extremely difficult and time consuming to individually study all hence simplify systematize their compounds they are classified into groups periods early models dobereiner s triads arranged three with order increasing atomic masses called triad he showed mass middle element approximately arithmetic mean other two but could identify only following from known at drawbacks this system was not found useful newlands law octaves according when placed physical chemical every th repetition first compared these series eight notes musical scale sa do re ga mi ma fa pa so da la ni ti h li b c n o f na mg al si p cl k ca cr mn fe co cu zn y as se br rb sr ce zr limitations applicable up calcium for lighter after eighth did possess newland adjusted slot e g different example fluorine chlorine bromine...