Why do atoms within a group have similar properties

What is a possible quantum number set for an electron in the 3s orbital of a magnesium atom

In a ball-and-stick molecular model, what do the sticks represent?

A2-kg bowling ball is 1 meter off the ground on a post when it falls. just before it reaches the ground, its traveling 4.4 m/s. assuming that there is no air resistant, which statement is true a. the initial potential energy is less then the final kinetic energy b. the mechanical energy is not conserved c. the mechanical energy is conserved d. the initial potential energy is greater than the final kinetic energy