23.9 cm^3 of barium hydroxide solution required exactly 25.0^3 of 0.0871 mol dm^3 nitric acid for complete neutralization. Calculate the molar concentration of the barium hydroxide solution by carrying out the following steps:

a) Calculate the number of moles of nitric acid used in this titration
b) Calculate the number of moles barium hydroxide in 23.9 cm^3 of solution using the equation to provide a link from a)
c) Now calculate the molar concentration of the barium hydroxide

Your answers seem great so far, except for a tiny issue: With the ionic symbols, try to get into the habit of using "+", with metals, like sodium, and try to use the integer first. So, for example, a potassium ion would be K^+, while an oxide ion would be O^2-

Let's take aluminium as an example I'll work through:

Aluminium, with it's atomic number of 13, will have an electronic configuration of 1s2 2s2 2p6 1s2 2p1. So it would have 2, 8, 3 electrons in the first three energy levels, respectively.

Usually, if an elemental atom has a valence electron (highest energy level electron) count less than 4, it almost always will lose electrons. Since aluminium has 3, it will also lose the electrons.

It loses the 3 valence electrons, and so will end up with 10 electrons.

Since the atomic number also tells how many protons it has, we know that an aluminium atom has 13 protons, which doesn't change.

Since the size of the charges of a proton and an electron are the same, with protons being positive and the electrons being negative, an aluminium ion would have a charge of +3, and the Ionic symbol would be Al^3+

Hope I helped! xx