4. Describe the differences in the atomic structures of a hydrogen atom and a helium atom

A helium atom consists of a nucleus containing two positively charged protons and two neutrons, encircled by two orbiting electrons which carry a negative charge. A hydrogen atom has just one proton and one electron. The difference is that the nucleus is 4.1 times heavier than normal.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.

the answers would be

the first one and the second one