Question

what ions are predictable charge ions? name two cations and two anions that the charge is known and why the charge is known.

Answer 1

Ions with predictable charges are those whose charges we can predict.

from the atomic no of an atom we come to know the electron no.and from the electron no. electronic configuration is written.then from the valence electron/electrons we can easily come to know the valency ,group and the most stable ion formed by an atom.

Usually most of the elements in a group (formed by atoms with same valence electrons) have same stable ion but exception occurs lots of time.

but we can predict the charges over alkali metals,alkaline earth metals (except Be),Alluminium,Nitrogen,Oxygen group,Halogen group.

Example of two cations:Na+

the charge over Sodium is +1 as it has an atomic no of 11 and electronic configuration is

[Ne₁₀]3s¹ .So, the 1 valence Electron is 3s-orbital.after loosing this Sodium will have a stable nearest inert gas like electronic configuration and Na will form Na⁺ ion.So the predictable charge on Sodium is (+1).

2. Mg²⁺:

The charge over Magnesium is +2 as it has an atomic no of 12 and electronic configuration is

[Ne₁₀]3s²   .So, the 2 valence Electrons is 3s-orbital.after loosing these Magnesium will have a stable nearest inert gas Neon like electronic configuration and Mg will form Mg²⁺ ion.So the predictable charge on Magnesium is (+2).

Example of Anion:

1.O^2-:

The charge over Oxygen is -2 .s it has an atomic no of 8 and electronic configuration is

[He₂]2s²2p⁴ .So, there are 6 valence Electrons.Oxygen can either loose these 6 electrons to have a stable electronic configuration like Hellium or can gain 2 more electrons to have a stable electronic configuration like nearest noble gas Neon(10).But gaing only 2 electrons is more preferable than loosing 6 electrons.So,Oxide will have a stable nearest inert gas Neon like electronic configuration (vallence elctronic configuaration is 2s²2p⁶) and O will form O^2- (Oxide) ion.So the predictable charge on Oxygen is (-2).

2.F^-:

The predictable charge over Fluorine is -1 .s it has an atomic no of 9 and electronic configuration is

[He₂]2s²2p⁵ .So, there are 7 valence Electrons.Fluorine can either loose these 7 electrons to have a stable electronic configuration like Hellium or can gain 1 more electrons to have a stable electronic configuration like nearest noble gas Neon(10).But gaing only 1 electrons is more preferable than loosing 7 electrons.So,Fluoride will have a stable nearest inert gas Neon like electronic configuration (vallence elctronic configuaration is 2s²2p⁶) and F will form F^- (Fluoride) ion.So the predictable charge on Fluorine is (-1).