Radioisotopic ages of newly discovered fossil sites hold clues to evolution of mammals
Anatolia, the western part of modern-day Turkey that sits at the crossroads of Asia, Africa, and Europe, is a fossil-rich ...
C&EN1y
Lesson 4.3: The Periodic Table and Energy-Level Models
After the third energy level has 8 electrons, the next electron goes into the fourth level. 4th Period: Potassium and Calcium—Electrons go into the fourth energy level. A small piece of sodium metal ...