When drawing the 'dot and cross' diagram to show the ionic bonding in aluminium oxide, Al2O3, do we place the nos "2" and "3" in front of the brackets containing the 'dot and cross' diagram, e.g 2[Al]3[O]?
I notice that some books place the "2" and "3" as subscripts while others place the nos. in front.
What is meant by a covalent bond
In the "dot and cross" diagram for aluminium oxide (Al2O3), you would typically place the numerical subscripts as subscripts after the chemical symbols, indicating the number of each element present in the compound. Therefore, it would be written as Al2O3 without any brackets.
The subscript numbers should not be placed in front of the brackets containing the "dot and cross" diagram. This notation is used for indicating the ratio of elements within the compound, rather than representing the structure itself.
When representing the ionic bonding in compounds like aluminium oxide (Al2O3) using the 'dot and cross' diagram, it is common practice to place the numerical subscripts outside of the brackets. This helps to clearly indicate the ratio of ions present in the compound.
In the case of aluminium oxide, there are two aluminium ions (Al3+) and three oxide ions (O2-) present. The 'dot and cross' diagram for aluminium oxide can be represented as:
2[Al]3[O]
This shows that there are two aluminium ions and three oxide ions in the compound.
However, it is worth noting that different sources or books may present this differently. Some might use subscripts within the brackets, while others may use the numerical subscript outside the brackets. The important thing is to understand the concept and ratio being portrayed, whether the subscripts are inside or outside the brackets.
The link provided by SraJMcGin refers more to the cross product of mathematics than to your question.
What you want to do with ionic compounds is to show
2Al+3 + O-2 with two pairs of electrons on the left, top, right, and bottom of the O. I can't draw them on the board. The other way of doing it is to show one Al ion with another just below it, then to the right show 3 O atoms, one above the other, and put in the dots and crosses on the O. Don't forget to put the -2 charge on each oxygen when you have finished.