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first 20 elements with valency and atomic number first 20 elements with atomic mass and valency and atomic number first 20 elements of periodic table with valency and atomic number first 20 elements with symbols and atomic number and valency first 20 elements with atomic number and electronic configuration and valency write first 20 elements with symbols atomic number and valency in a creative way first 20 elements of periodic table with atomic mass and atomic number and valency what is the valency of first 20 elements
