No, atoms cannot be directly seen using a regular optical microscope due to their extremely small size. The size of an atom is on the order of a few tenths of a nanometer (10^-10 meters), which is far smaller than the wavelength of visible light (around 400-700 nanometers). As a result, the resolution limit of an optical microscope, determined by the diffraction of light, prevents us from directly observing individual atoms.
Traditional optical microscopes use visible light and lenses to magnify objects, but their resolution is limited by the wave nature of light. This limitation is known as the diffraction limit, which states that the minimum resolvable distance is approximately half the wavelength of light used. Since the size of an atom is much smaller than the wavelength of visible light, it is not possible to see atoms directly with an optical microscope.
To observe atoms, specialized techniques such as electron microscopy, scanning probe microscopy, or advanced imaging techniques like scanning tunneling microscopy (STM) and atomic force microscopy (AFM) are used. These techniques utilize different principles, such as the interaction of electrons or the probe tip with the sample, to achieve atomic-scale resolution.