Nguyên tố X có 2 đồng vị là X1 và X2 .tổng số hạt của không mang điện của X1 và X2 lá 90 . Nếu cho 1,2 g 20Ca tác dụng với 1 lượng X vừa đủ thì được 5,994 g hợp chất .biết tỉ lệ giữa số nguyên tử X1 và X2 bằng 605:495 .tính nguyên tử khối trung bình của X , số khối của X1 ,X2 . có bao nhiêu nguyên tử X1,X2 trong một mol nguyên tử x

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