One isotope of a metallic element has mass number 10 and has 7 neutrons in the nucleus. It forms an atomic ion having 2 electrons. Enter the symbol for this ion

Mass # 10 means protons + neutrons = 10. If it has 7 neutrons, then protons must be 10-7= 3. Atomic number 3 must be Li. So # electrons in the neutral element must be 3. If the element has just two electrons then the charge of the ion must be +1 so the symbol is Li^1+.

To determine the symbol for the ion, we need to know the atomic number and the charge of the ion. The atomic number is the number of protons in an atom, which is equal to the number of electrons in a neutral atom.

Given that the isotope has a mass number of 10, it means it has 10 nucleons (protons + neutrons). It also tells us that there are 7 neutrons. Therefore, the number of protons is 10 - 7 = 3.

Now, we know the atomic number is 3, and the ion has 2 electrons. When an atom loses electrons, it becomes positively charged. So with 2 electrons, this ion has a charge of +2.

To indicate the charge in the chemical symbol, we write it as a superscript after the symbol. So for this ion, the atomic symbol is written as follows:

Symbol + Charge
3+2

The symbol for the ion is then Li2+.