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 ...

Water is essential to keep hydrated and to prevent ... Bone density decreases with age, particularly in women. A good intake of calcium is required to help maintain bone mass, and reduce the ...

S ome people prefer to drink bottled water rather than tap water because their tap water isn’t “clean enough.” That’s the main draw of bottled water: It’s already filter ...