If two atoms have different atomic number. are they the same element or an isotope?

Which traits do human embryos have that link them to a common ancestor with fish and reptiles? a. scales and tail b. gill slits and scales c. tail and gill slits d. hair and tail

This is a characteristic of the elements in the periodic table that shows a pattern. it may increase or decrease across or down the table.

Give the orbital configuration of the phosphorus (p) atom.