Which of the following substances are diamagnetic?
Bi, Al, Na, Cu, Ca and Ni.

Explanation

To determine which of the given substances are diamagnetic, we need to understand the properties of diamagnetic materials. Diamagnetic substances are characterized by the absence of unpaired electrons, which means they do not have a net magnetic moment. When placed in a magnetic field, they are weakly repelled.

Here’s a step-by-step solution:

### Step 1: List the given substances
The substances provided in the question are:
- Bi (Bismuth)
- Al (Aluminum)
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