To determine which molecule could be the product of a reaction yielding atoms with stable configurations, we should look for molecules that consist of atoms producing a full outer electron shell, which generally means they are bonded to achieve this stability.
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CaBr2 (Calcium bromide): Calcium (Ca) has 2 valence electrons and typically loses them to form a stable ion (Ca²⁺). Bromine (Br) has 7 valence electrons and gains 1 electron to become Br⁻. In CaBr2, calcium loses 2 electrons while each bromine gains 1, leading to a stable ionic compound.
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SiO5: Silicon (Si) has 4 valence electrons and typically forms 4 bonds, but it is unlikely that it would form a stable compound with 5 oxygen atoms in typical conditions.
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NaCl2 (Sodium chloride): Sodium (Na) has 1 valence electron and typically forms a stable ion (Na⁺) by losing that electron. However, NaCl2 suggests sodium bonds with 2 chloride ions. This is unconventional, as sodium typically forms a 1:1 ratio with chlorine, leading to NaCl. Therefore, NaCl2 is not stable.
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PH4 (Phosphine): Phosphorus (P) has 5 valence electrons and can form up to 5 bonds, but PH4 does not represent a highly stable molecular species. Phosphorus usually does not expand its valence shell in this way with hydrogen.
Based on this analysis, the most reasonable product with a stable configuration is CaBr2. It forms a stable ionic compound where the calcium ion and bromide ions achieve full outer electron shells, making it the best choice among the options provided.