Question

write the chemical symbols for three different atoms or atomic cations with 11 electrons.

Explanation:

Step1: Recall atomic structure basics

In a neutral atom, the number of electrons is equal to the atomic number. For cations, the number of electrons is less than the atomic number by the charge value.

Step2: Identify neutral atom with 11 electrons

Sodium (Na) has an atomic number of 11. In its neutral state, it has 11 electrons. So one symbol is Na.

Step3: Consider cations with 11 electrons

Magnesium has an atomic number of 12. A magnesium - 1+ cation ($Mg^{+}$) has 12 - 1=11 electrons.
Aluminum has an atomic number of 13. An aluminum - 2+ cation ($Al^{2 +}$) has 13 - 2 = 11 electrons.

Answer:

Na, $Mg^{+}$, $Al^{2+}$