Selah is making a mobile of an atom of beryllium to hang from the ceiling in her science class. She uses a clear plastic bag for the nucleus and fills it with white foam balls for protons and black foam balls for neutrons. She suspends blue foam balls from strings around the nucleus to represent the electrons. Which diagram shows Selah's model?

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Explanation:

The question is incomplete because the images of the models are absent. However, i will try to give you a general description of what the correct answer should be.

Beryllium is a member of group 2 in the periodic table. Beryllium has an atomic number of 4. This implies that it has four protons in its nucleus and four electrons in its shells. In a neutral atom, the number of electrons on the shells is equal to the number of protons in the nucleus.

The electronic configuration of Beryllium is 1s2 2s2. This implies that it should have two shells each containing only two electrons each.

Since we are using white foam balls for protons and black foam balls for neutrons, the clear plastic will contain four white foam balls and five  black foam balls since the mass number of beryllium is 9 and number of neutrons = mass number - number of protons.

Four blue foam balls hanging from strings will represent the electrons around the nucleus.

Any model that corresponds to the description above is the correct answer.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.