Which atoms have the same number of neutrons?
which is the correct answer and why?
1.h-1 and he-3
2. h-2 and he-4
3. h-3 and he- 3
4. h-3 and he-4

4. H-3 and He-4

Explanation:

H-3 means hydrogen with a mass number of 3. Mass number is the addition of protons and neutrons in the nucleus. Hydrogen always has 1 proton because it has atomic number 1, therefore the number of neutrons is found by subtracting 1 from the mass number (3).

3-1= 2 neutrons

He-4 also has 2 neutrons. He-4 has mass number 4, which means that its protons and neutrons added together equals 4. Helium has 2 protons because it has atomic number 2.

Therefore 2 + neutrons =4

neutrons =4-2

neutrons =2