The nuclei for several common isotopes of hydrogen, helium, lithium and beryllium are displayed. Which nucleus has the same number of up quarks as down quarks?
- A$^1_1\text{H}$
- B$^2_2\text{He}$
- C$^7_3\text{Li}$
- D$^9_4\text{Be}$
Physics 9702 · AS & A Level · Fundamental particles