The two are potassium and rubidium. Why? Na is an alkali metal. As you go down the metals become more reactive.
Calcium has 20 protons. Why? The atomic # is 20 (the one at the top).
It has 20 neutrons. Why? The atomic mass (the number on the bottom) is ~40, ignoring electron mass. 40- 20 protons = 20 neutrons.
It has 20 electrons.
Why? The # of protons and electrons is the same. Ions aren't on the periodic table.
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Coevolution happens when the genetic development between two or more species affects the evolution of each other. An example would be hummingbirds and bird-pollinated (ornithophilous) flowers. The ornithophilous flowers give nourishment to the birds with their nectar that has high sugar content. The birds in return aids in the pollination of these flowers.
If a burning splint is placed in a container and burns more brightly in the presence of some gas already in the cylinder, that gas would probably be Oxygen.
Oxygen is the main component of air that we need to breathe. It is the most commonly available oxidizer. Besides combustion, it plays many roles in our life such as; the food we eat requires oxygen which helps in digestion and absorption of nutrients by the cells.
<span>prorostomes and deuterostomes is your answer</span>
Answer: A. Average rainfall has decreased
Explanation:
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