A)Calcium-This because calcium has two valence electrons hence it is a metal therefore it will form an ionic bond with carbon.
<u>Answer:</u> The standard enthalpy change of the reaction is -1076.82kJ
<u>Explanation:</u>
Enthalpy change is defined as the difference in enthalpies of all the product and the reactants each multiplied with their respective number of moles. It is represented as 
The equation used to calculate enthalpy change is of a reaction is:
![\Delta H^o_{rxn}=\sum [n\times \Delta H^o_f(product)]-\sum [n\times \Delta H^o_f(reactant)]](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Brxn%7D%3D%5Csum%20%5Bn%5Ctimes%20%5CDelta%20H%5Eo_f%28product%29%5D-%5Csum%20%5Bn%5Ctimes%20%5CDelta%20H%5Eo_f%28reactant%29%5D)
For the given chemical reaction:

The equation for the enthalpy change of the above reaction is:
![\Delta H^o_{rxn}=[(1\times \Delta H^o_f_{(CO_2)})+(2\times \Delta H^o_f_{(SO_2)})]-[(1\times \Delta H^o_f_{(CS_2)})+(3\times \Delta H^o_f_{(O_2)})]](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Brxn%7D%3D%5B%281%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28CO_2%29%7D%29%2B%282%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28SO_2%29%7D%29%5D-%5B%281%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28CS_2%29%7D%29%2B%283%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28O_2%29%7D%29%5D)
We are given:

Putting values in above equation, we get:
![\Delta H^o_{rxn}=[(1\times (-393.52))+(2\times (-296.8))]-[(1\times (89.70))+(3\times (0)]\\\\\Delta H^o_{rxn}=-1076.82kJ](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Brxn%7D%3D%5B%281%5Ctimes%20%28-393.52%29%29%2B%282%5Ctimes%20%28-296.8%29%29%5D-%5B%281%5Ctimes%20%2889.70%29%29%2B%283%5Ctimes%20%280%29%5D%5C%5C%5C%5C%5CDelta%20H%5Eo_%7Brxn%7D%3D-1076.82kJ)
Hence, the standard enthalpy change of the reaction is -1076.82kJ
Think of it this way: say orbitals are boxes and each box can contain 2 electrons.
If there are 3 boxes forming one orbital, it takes 6 electrons to completely fill it. Since there's less than six, each box takes one electron, so there's 1 electron per orbital.
Answer:In the chemical formula Al2(SO4)3, the Al2 means there two aluminium (atoms or ions). The SO4 is a sulfate ion and (SO4)3 means there are 3 sulfate ions. The number 3 before Al2(SO4)3 means there are three times the number of atoms and ions of the chemical formula.