Number of neutrons = mass number - atomic number = 40 - 19 = 21 answer
At room temperature the air is Gas
The amplitude of a wave is the distance between a point on one wave and the identical point on the next wave. The period and wavelength of a wave are inversely proportional.
Wave particle duality is the concept in quantum mechanics that every particle or quantum entity may be described as either a particle or a wave. It expresses the inability of the classical concepts "particle" or "wave" to fully describe the behaviour of quantum-scale objects.
