Using evidence to support explanations is a good practice because it proves that what you are explaining can be verified.
I think the answer you are looking for is D.
Hope this helps!!! :D
Explanation:
Chlorine atom has an atomic number of 17
Electronic configuration
Cl = 1s2 2s2 2p6 3s2 3p5
Cl- = 1s2 2s2 2p6 3s2 3p6
Soduim atom has an atomic number of 11
Electronic configuration
Na = 1s2 2s2 2p6 3s1
Na+ = 1s2 2s2 2p6
Calcium atom has an atomic number of 20
Electronic configuration
Ca = 1s2 2s2 2p6 3s2 3p6 4s2
Ca2+ = 1s2 2s2 2p6 3s2 3p6
An example of an exothermic reaction will be formation of ice
You would observe, trying to identify if there's a minimum difference in each beaker. Like, colour, or using an <em>bagueta </em>(idk how to say it in english), churning it or something like that.
