Which BEST explains why the Earth has layers? A. The Earth's layers formed because the heaviest materials (like iron and nickel) float on top of the lighter materials that make up the frost.
B. The Earth's layers formed because the heaviest materials (like iron and nickel) sink below the lighter materials that make up the crust.

B

Explanation:

I know im right I forgot some of the lessons cause this was still in grade 3 now Im grade 6

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

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since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.