Answer:
A
Explanation:
The answer A is the best answer because it contains the most general characteristic of a chemical change.
Answer:
Ba(ClO₃)₂ → BaCl₂ + 3 O₂ <em>Descomposition. </em>
CaO + CO₂ → CaCO₃ <em>Combination. </em>
NaNO₂ + HCl → NaCl + HNO₂ <em>Double replacement. </em>
Mg + ZnSO₄ → MgSO₄ + Zn <em>Single replacement. </em>
Explanation:
A combination reaction is defined as a reaction in which two or more substances combine to form a single new substance.
A + B → AB
A descomposition reaction is defined as a reaction in which a compound breaks down into two or more simpler substances.
AB → A + B
A double replacement is a chemical reaction were the positive and negative ions of two ionic compounds exchange places to form two new compounds.
AB + CD → AD + CB
A single replacement is another type of reaction were one element replaces a similar element in a compound.
A + BC → AC + B
Thus, with this information it is possible to classify these reactions as:
Ba(ClO₃)₂ → BaCl₂ + 3 O₂ <em>Descomposition. </em>One single molecule breaks down into two or more molecules
CaO + CO₂ → CaCO₃ <em>Combination. </em>Two substances are combined to form one single molecule
NaNO₂ + HCl → NaCl + HNO₂ <em>Double replacement. </em>Na and H are exchange places to form two new compounds
Mg + ZnSO₄ → MgSO₄ + Zn <em>Single replacement. </em>Mg is replacing Zn.
I hope it helps!
Answer: The statement the 
shell holds a minimum number of 
electrons is true.
Explanation:
The alphabet 'n' denotes the principal quantum number whose value can be equal to 1, 2, 3, and so on but can never be zero.
Basically, 'n' is the number of shell of an atom and total number of orbitals present in a shell is 
.
Each orbital can hold up to a maximum of wo electrons. Hence, the shell can hold a minimum number of electrons.
Thus, we ca conclude that the statement the shell holds a minimum number of electrons is true.
