Iron is a transition metal with an atomic number of 26.
What is the ground-state electronic configuration of the iron(II) ion, Fe2+\text{Fe}^{2+}Fe2+?
1s22s22p63s23p63d44s21s^2 2s^2 2p^6 3s^2 3p^6 3d^4 4s^21s22s22p63s23p63d44s2
1s22s22p63s23p63d61s^2 2s^2 2p^6 3s^2 3p^6 3d^61s22s22p63s23p63d6
1s22s22p63s23p63d54s11s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^11s22s22p63s23p63d54s1
1s22s22p63s23p63d64s21s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^21s22s22p63s23p63d64s2
87 exam-style questions on Edexcel GCSE Chemistry 2.1 Atomic structure, covering 2.1.1 Development of the atomic model, 2.1.2 Structure of the atom and subatomic particles, 2.1.3 Mass number, isotopes and relative atomic mass, and 2.1.4 Calculating relative atomic mass from isotopic abundance. Each one has a worked solution and a mark scheme showing where the marks go.