How do work out what the empirical formula for aluminium selenide is?
You need to provide the data. It's easier to explain with numbers than try to go through it with words. You do you not have numbers? Perhaps the question is, "How do we know what the formula of aluminum selenide is?"
To determine the empirical formula of a compound like aluminum selenide, you need to know the relative number of atoms of each element present in the compound.
One way to obtain this information is through experimental data, such as the mass of each element or the percentage composition. However, without any given data, let's approach this question conceptually.
The empirical formula represents the simplest whole number ratio of atoms in a compound. In the case of aluminum selenide, we know that aluminum (Al) is a metal, while selenium (Se) is a nonmetal.
1. Determine the charges: Aluminum typically forms a +3 ion (Al3+), while selenium can form a -2 ion (Se2-).
2. To balance the charges, we need two aluminum ions for every three selenium ions. This yields a compound with a 2:3 ratio of aluminum to selenium.
Therefore, based on this conceptual approach, the empirical formula for aluminum selenide would be Al2Se3. However, it is important to note that actual experimental data or any additional information about the compound would provide more accurate results.