Tìm nguyên tố X( tên và ký hiệu)biết a) Nguyên tử X năng gấp 2 lần nguyên tử nguyên tố Oxi b)Nguyên tố X có nguyên tử khối 3,5 lần nguyên tử khối Oxi c)4 nguyên tử Magie năng bằng 3 nguyên tử nguyên tố X d)19 nguyên tử X năng bằng 11 nguyên tử Flo e) 3 nguyên tố X năng gấp 8 nguyên tử C f) 3 nguyên tử X năng gấp 16 nguyên tử C g) Nguyên tử X năng bằng tổng khối lượng của 2 nguyên tử Magie và lưu huỳnh

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