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The atomic mass of an element is 19. The second shell of its atom contain 7 electrons. The number of protons in its nucleus is : (1) 9 (2) 10 (3) 7 (4) 12 |
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Answer» Correct option (1) 9 Explanation: Element (19/9 X) K L X = 2 , 7 The sum of the number of electrons in shell K & L of element X is 9 Therefore, number of protons in element X is 9. |
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