What particle is needed to complete the following equation?

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.

How many neutrons does an element have if its atomic number is 50 and its mass number is 166

Which type of intermolecular force is pbr3