Answer: The carbon atoms that form acetylene are sp hybrid, which has more S component (1/2s component) than sp2 hybrid carbon atoms in ethane and ethylene, and the electron cloud is closer to the nucleus. The electronegativity of the carbon atom in the sp hybrid orbit is greater than that of the other two hybrid carbon atoms, which makes the electron pair of acetylene carbon-hydrogen σ bond closer to the carbon atom side. Hydrogen atom lacks electrons and is acidic, which is easy to substitute with metals such as Ag, Cu and Na.