Chemistry · Structure of atom

Which of the following pairs represents a pair of isobars?

1. \( {}^{12}_{6}\text{C} \) and \( {}^{14}_{6}\text{C} \)
2. \( {}^{1} _{1}\text{H} \) and \( {}^{2}_{1}\text{H} \)
3. \( {}^{35}_{17}\text{Cl} \) and \( {}^{37}_{17}\text{Cl} \)
4. \( {}^{14}_{6}\text{C} \) and \( {}^{14}_{7}\text{N} \)