Question

Magnesium has atomic number 12. Write the number of electrons and protons that are present. What kind of ions will it form? Write the formula.

Answer 1

Hint: Number of electrons and protons are equal to the atomic number of a neutral atom. Magnesium is an alkaline earth metal and so metals are electropositive in nature. Magnesium can easily lose two electrons to achieve the nearest noble gas configuration.

Complete answer:
We can see that in the question, it has been given that the magnesium is having an atomic number of 12, we need to find the number of electrons and protons in it. For a neutral atom, Atomic number (Z) is the number of protons or electrons or neutrons present in an atom. Since in a neutral atom, in order to balance the charge, an equal number of protons and electrons should be there.
Therefore, the number of protons present in Magnesium is 12 and the number of electrons present in Magnesium is also 12. Then, the next part of the question is about the kind of ions that will be formed by Magnesium. As we know that the Atomic number of Magnesium is 12, which indicates the position in the periodic table . Magnesium is in group 2 and in period 3. As magnesium is in group 2 , we got to know that it belongs to the alkaline earth metals.
We know that metals are electropositive in nature. I.e, they can readily lose electrons from their valence shell. So, Magnesium has an electronic configuration of ${ \left[ Ne \right] { 3s }^{ 2 } }$ . So, by losing two electrons from its outermost ‘s’ subshell, it can attain the stable nearest noble gas configuration which is${ 1s }^{ 2 }{ 2s }^{ 2 }{ 2p }^{ 6 }$ .
So, Magnesium loses two electrons to form a positively charged ion, cation and its formula is ${ Mg }^{ 2+ }$ .
When an atom gains electrons , it forms an ion named ‘anion’ and when an atom loses electrons, it forms an ion named ‘cation’. Anions are represented by the chemical formula of the element raised to the power of the number of electrons gained along with a negative charge. Cations are represented by the chemical formula of the element raised to the power of the number of electrons lost along with a positive charge.
Therefore, we can conclude that the number of electrons and protons present in Magnesium is 12 and 12 respectively. And Magnesium forms a positively charged ion ,cation , whose formula is ${ Mg }^{ 2+ }$.

Note: Number of electrons = number of protons = atomic number (Z), this works only in case of neutral atoms. In the case of ions, the number of protons will be equal to atomic number, but the number of electrons won’t be equal to atomic number. It is because in the case of anions and cations, the electrons are gained or lost from the neutral atom, and the number of protons remains the same for both parent atom and the ions.