Question 19 of 25 The atomic number of the element radium is 88. How many neutrons does radium-226 have? A. 98
B. 138
C. 88
D. 116
E. 226
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B. 138

Explanation:

Based on isotope notation:

For the atom A, the mass number, X, is the sum of neutrons and protons and

n is the number of protons = Atomic number.

The number of protons depends of the nature of the atom. For example, Carbon has 12 protons, hydrogen 1 and Radium has 88 protons.

The radium-226 means the mass number is 226. Thus, number of neutrons are:

Mass number - Atomic number

226 - 88 = 138

Right answer is:

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