Which element has
two shells, both of which are completely filled with electrons?

Explanation

To determine which element has two shells, both of which are completely filled with electrons, we can follow these steps:

### Step 1: Understand Electron Shells
- The first shell (K shell) can hold a maximum of 2 electrons.
- The second shell (L shell) can hold a maximum of 8 electrons.

### Step 2: Identify the Total Number of Electrons
- For both shells to be completely filled, we need:
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