Answer: A completely filled 3d10 is extra stable, as is d5.
- A A completely filled 3d10 is extra stable, as is d5
- B 3d orbitals are always lower in energy than the 4s orbital
- C The 4s orbital is filled before the 3d orbital in every transition metal
- D Copper's odd atomic number forces an unpaired 4s electron
Correct answer: A. A completely filled 3d10 is extra stable, as is d5
Explanation: A fully filled 3d10 subshell (like half-filled d5) has extra stability due to symmetrical electron distribution and exchange energy.
The complete modern periodic table (118 elements). Image: Cepheus et al., Public Domain, via Wikimedia Commons.
Concept context
The periodic table organises all 118 elements by atomic number and similar properties. Study periodic trends like atomic radius, ionization energy, and electronegativity, and learn how an element's position predicts its behaviour.
Read the full Classification of Elements and Periodicity in Properties notes →