Answer:
Substance at the beginning of a reaction- reactant
Substance at the end of a reaction- product
Number placed before a compound in a chemical equation- stoichiometric coefficient
Explanation:
In a reaction equation, the species written on the left hand side of the equation are called the reactants.
The reactants combine to form the species on the right hand side of the reaction equation called products.
The stoichiometric coefficient is a number written before the formula of a compound in the reaction equation.
S and S²⁻ do not have the outer subshell fully filled with electrons.
Explanation:
We look at electronic configurations:
Ca 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² - the outer subshell 4s² is fully-filled with electrons
S 1s² 2s² 2p⁶ 3s² 3p⁴ - the outer subshell 3p⁴ is not fully-filled with electrons
Zn²⁺ 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s⁰ - here the 4s subshell is higher in energy than 3d subshell so will consider 3d¹⁰ the out subshell which is fully-filled with electrons
S²⁻ 1s² 2s² 2p⁶ 3s² 3p² - the outer subshell 3p² is not fully-filled with electrons
Ca²⁺ 1s² 2s² 2p⁶ 3s² 3p⁶ - the outer subshell 3p⁶ is fully-filled with electrons
Learn more about:
electron configurations
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Im pretty sure it nitric acid