A neutral isotope of an element contains 21 electrons and 24 neutrons.What is the following representation for this nucleus?

Question

Quizplus · Accepted Answer

The element is specified to be neutral, so it must have the same number of protons as electrons. Therefore, it has atomic number 21. The isotope also contains 24 neutrons, which are found by subtracting the atomic number from the mass number. The mass number is the sum of protons and neutrons, so it is 21 + 24 = 45.

The representation for this nucleus is: 
21 protons -> 11 electrons + 10 alpha characters (using the symbol for the element) -> _5ef1_4382_842f_83d5831bd770_TB5752_11

The correct answer is B because it matches this format.

A Neutral Isotope of an Element Contains 21 Electrons and 24