The element radium has a mass number of 226 and an atomic number of 88. How many neutrons does an atom of radium have?(1 point)
A. 138
B. 314
C.88
D. 226
A. 138
The atomic number of an element represents the number of protons in its nucleus. In this case, the atomic number of radium (Ra) is 88. The mass number of an element represents the sum of protons and neutrons in its nucleus. In this case, the mass number of radium is 226.
To find the number of neutrons in an atom of radium, we subtract the atomic number from the mass number.
Number of neutrons = Mass number - Atomic number
Number of neutrons = 226 - 88
Number of neutrons = 138
Therefore, the correct answer is A. 138.
To determine the number of neutrons, you need to subtract the atomic number from the mass number.
In this case, the atomic number of radium is 88, which represents the number of protons in its nucleus. The mass number is 226, which represents the total number of protons and neutrons in the nucleus.
To find the number of neutrons, subtract the atomic number (88) from the mass number (226):
226 - 88 = 138
Therefore, the answer is A. 138.