Calculate the lithium ion (Li+) concentration for a 0.821 M Li2S solution.

The lithium ion[Li⁺]=1.642 M

Ionic compounds will dissociate into ions when dissolved in water. The strength of the dissociation depends on the strength of the electrolyte properties. The stronger it is, the more ions will dissociate

Reaction

Li₂S⇒2Li⁺+S²⁻

mol ratio Li₂S : Li⁺: S²⁻ = 1 : 2 : 1

so the lithium-ion (Li⁺) concentration :

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.