The atomic number of an element represents the number of protons in the nucleus of an atom of that element. In this question, it is stated that there are six protons in the atom. Therefore, the atomic number of the element is 6.

Now let`s analyze the other options:

Option 2: The atomic number cannot be 12 because there are only six protons in the atom, not twelve.

Option 3: The atomic number cannot be 18 because there are only six protons in the atom, not eighteen.

Option 4: The atomic number cannot be 24 because there are only six protons in the atom, not twenty-four.

Therefore, the correct answer is option 1, which states that the atomic number of the element is 6.