Question

there is no Air on the Moon why

Answer 1

because moon has no atmosphere like earth

Answer 2

The Apollo science packages on the Moon detected an extremely thin atmosphere - “thin” as in, it’s as tenuous as the Earth’s atmosphere at the altitude at which the International Space Station orbits! This was a major surprise, and even stranger were the constituents of the Moon’s atmosphere - it includes helium, argon, and possibly neon, ammonia, methane and carbon dioxide. Oddly, there is also potassium and sodium, which we don’t see in the atmospheres of any of the terrestrial planets. But as others have answered, the Moon’s gravity and exposure to the solar wind prevent the Moon from holding on to anything we would regard as a true atmosphere, in common with most of the moons of the solar system. Saturn’s moon Titan is the only moon in the solar system which has a dense atmosphere.