To determine which is paramagnetic.
Recall that for:
• diamagnetic: all of the electrons are paired
• paramagnetic: at least one electron is unpaired
Note that for a neutral element, Atomic Number = # of protons = # of electrons.
Step 1: Electron configuration
The atomic number of Ca is 20, which means Ca has 20 e–.
The noble gas before Ca is Ar (18 e–).
The shorthand e– config. for Ca is: Ca: [Ar]4s2
Step 2: Orbital diagram
The outermost sublevel is 4s. Recall that the s sublevel contains 1 orbital.
When filling up the orbitals, take note of:
• Aufbau Principle: totally fill in the lowest energy orbital first
• Hund’s Rule: electron orbitals that are degenerate (same energy orbital) are first half-filled before they are totally filled
The orbital diagram for Ca is:
Which of the following is paramagnetic?