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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Answer:1. not enough natural ingredients like food and water, 2. the people your are surrounded in the environment, 3. the laws or rules that apply to living in gov./environment
Explanation:
1. maybe there aren't enough local stores in your area and you have to walk or drive miles just to get there, 2. maybe you have some connotation with people around you, or they themselves are setting good examples for you or your family, the community is too crowded, 3.maybe you want to leave a country because the system doesn't work for you, discrimination laws or a form of unfairness and mistreatment. maybe too intrusive.
The rock erodes over time and creates soft, supple material which we refer to as soil
