Complete the table to show the maximum number of electrons in each shell1 2 3 4Up to calciumBigger than calcium

The maximum number of electrons that can be held in each shell is determined by the formula 2n^2, where n is the energy level or shell number.

1. For the first shell (n=1), the maximum number of electrons is 2*(1^2) = 2.
2. For the second shell (n=2), the maximum number of electrons is 2*(2^2) = 8.
3. For the third shell (n=3), the maximum number of electrons is 2*(3^2) = 18.
4. For the fourth shell (n=4), the maximum number of electrons is 2*(4^2) = 32.

However, for atoms up to calcium (atomic number 20), the distribution of electrons in the shells follows a slightly different rule due to the way the subshells are filled.

1. The first shell can hold up to 2 electrons.
2. The second shell can hold up to 8 electrons.
3. The third shell can hold up to 8 electrons for atoms up to calcium. For atoms bigger than calcium, the third shell can hold up to 18 electrons.
4. The fourth shell can hold up to 2 electrons for atoms up to calcium. For atoms bigger than calcium, the fourth shell can hold more electrons, but the exact number depends on the specific atom.