1. calculate the atomic mass of boron, which contains 18.83% of mass 10.016 amu and 81.17% mass 11.013 amu ?
2. what is the kinetic energy of a photoelectron ejected from cesium 500nm light?
3. explain why Li less electronegative that Be?
4. explain why a) Na doesn't normally from Na2+ ion. b) Cl doesn't from Cl2- ion.
5. explain why lattice energy of mgo is greater than ca0