H₂O + H₂O ⇌ H₃O⁺ + OH⁻
You use two single-barbed arrows pointing in opposite directions (technically rightwards harpoon over leftwards harpoon) <em>to indicate a reversible reactio</em>n.
equation is balanced when the number of molecules are the equal in both reacting side and the product side.
Li(s) + n2(g) ---> Li3n(s)
From the equation above the reaction is not balanced since the molecules are not equal in both reacting side and the product side.
The reaction is balanced by adding 6 in front of Li and 2 infront of Li3n
that is
6Li(s) + n2(g)-----> 2Li3n(s)
There’s no picture or description you need to add one
To make an electron jump into a higher level we basically need to provide them with the energy. This energy can be provided by heating or by striking the potassium surface with a high frequency monochromatic wave of light.