The value converted to be 2.86*10^5 angstroms. Each aluminum atom is about 1.48 angstroms, so we can divide. Assuming that each aluminum atom is stacked directly on another one (which they aren't, but we can't measure without making this assumption), we come up with 1.93 * 10^5 atoms thick. Basically it's 1.93 * 10^5
