The time period in which tyrannosaurus rex first appeared

Tyrannosaurus rex appeared in the late Cretacious era 66 - 65 million years ago.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

56 moles of   lieter in chemistry