Why does calcium belong to 4th period?

What is the state of a equilibrium of a coin lying on a flat table i? What do white corpuscles do? Are interactions positive negative or neutral? What are the four main groups? Who was the man that a Caribbean zoologist who specialises in aquatic ecology and the environment? Is adding water to pancake mix a physical or chemical change? Is heavy rain proper noun? How many moles of Cu2(CO3)3 can be made from 5.67 g K2CO3? Why are Alkali metals so reactive? What theory states that a divine being put life on earth? How are proteins distugushed from each other? What is 1800 times small than a proton? What herbs are said to help regulate your Blood Pressure? Is once a connective? What double membranes organelles specialize in ATP through cellular respiration? What is the difference between a solute and solvent? What happens when water changes from 80 degree Celsius to 120 degree Celsius? What does the pH of a dilution measure? Does the hair dryer evaporate water? What happens if stroke volume increases?