A model of a square single layer of material has a side length of 5.0 × 10-7 m. The layer contains identical atoms arranged in straight rows and columns. Each atom has a diameter of 0.25 nm0.25\ \mathrm{nm}0.25 nm and touches the adjacent atoms.
Calculate the total number of atoms in the layer.
103 exam-style questions on Edexcel GCSE Physics 6.1 Atomic structure and isotopes, covering 6.1.1 Structure of the atom, 6.1.2 Isotopes: atomic and mass number, 6.1.3 Sub-atomic particles: masses and charges, and 6.1.4 Electron orbits and energy changes. Each one has a worked solution and a mark scheme showing where the marks go.