Atoms are extremely small. A typical atom has a radius of about 1 × 10-10 m, which is 0.1 nanometres. Small molecules, made of just a few atoms joined together, are also about this size. We say they are of the order of 10-10 m.
The nucleus is much smaller still. A typical nucleus is about 10-14 m across, which is around ten thousand times smaller than the atom. 'Order of magnitude' means the nearest power of ten, so it lets us compare sizes without needing exact values.
Because 10-10 m is such a tiny distance, you cannot see an atom with the naked eye or even with a light microscope.
