<span>The ionic charge of Calcium (Ca) in calcium carbonate (CaCO3) is 2+. CaCO3 has a neutral ionic charge sin CO3 has a 2- charge.</span>
Answer : The question is to write the elements alphabetically and seperating them with commas.
So in this case for your question of Fireworks , K

,
The answer will be
K, N, O.
You have to just differentiate the elements and write them according to the alphabetical order.
Answer:
2 elements
Explanation:
Octane is composed of carbon and hydrogen atoms.
<span>(K⁺¹)2Cr(O⁻²)4
+1*2 +x-2*4=0
2+x-8=0
x=6
Oxidation number of Cr is +6.</span>