SSC
CHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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An atom has 5 protons, 7 neutrons and 5 electrons. What is the mass number of the atom?
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5
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7
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2
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12
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Explanation:
Detailed explanation-1: -The mass number of an atom with five protons and seven neutrons is 12.
Detailed explanation-2: -The symbol for magnesium is . Magnesium has an atomic number of 12 and a mass number of 24. So a magnesium atom has 12 protons, 12 electrons, and 12 neutrons.
Detailed explanation-3: -Carbon atoms with 7 neutrons have an atomic mass of 13 (6 protons + 7 neutrons = 13). These atoms are the isotope called carbon-13.
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