To analyze the statement regarding the reaction between magnesium and chlorine to form magnesium chloride (MgCl2), we can look at the basic principles of stoichiometry and the conservation of mass.
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Before the reaction: Let's assume we start with 1 magnesium atom (Mg) and 2 chlorine atoms (Cl) since MgCl2 consists of 1 magnesium and 2 chlorine atoms.
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After the reaction: We will have 1 magnesium atom and 2 chlorine atoms in the form of magnesium chloride (MgCl2).
Now, let's evaluate the statements:
A. There are just as many magnesium atoms after the reaction as there were before it.
- This statement is true because there is 1 magnesium atom before and after the reaction.
B. The number of magnesium atoms decreased in the chemical reaction.
- This statement is false because the number of magnesium atoms remains the same.
C. The number of chlorine atoms doubled in the chemical reaction.
- This statement is false because we start with 2 chlorine atoms and end up with 2 chlorine atoms in MgCl2, so it did not double.
D. There are only a third as many atoms after the reaction as there were before it.
- This statement is false. We started with 3 atoms (1 Mg + 2 Cl) and ended with 3 atoms (1 Mg + 2 Cl), so this comparison does not hold.
The correct answer is: A. There are just as many magnesium atoms after the reaction as there were before it.