Which of the following correctly describes a trend in atomic structure as you go down the elements in one group of the periodic table?
a: The atomic mass and the atomic number increase as you go down in the group.
b:The atomic mass increases and the atomic number stays constant as you go down in the group
c:The atomic mass stays constant and the atomic number increases as you go down in the group.
d:The atomic mass and the atomic number increase by 1 as you go down in the group.