This question has two parts. One calcium atom (element 20, Ca) reacts with two fluorine atoms (element 9, F) to produce Calcium Fluoride, CaF2. 19a) Do you think the bonds in calcium fluoride are more likely ionic or covalent? Why do you think this?
19b) Using the concept of valence electrons, explain why one calcium atom and two fluorine atoms react together.

In an exothermic reaction the bonding energy of the product is: less than the reactants same as the reactants greater than the reactants dependent upon the presence of a catalyst

What must occur for air masses to form fronts

Lab reagent, hypothesis test. a reference solution used as a lab reagent is purported to have a concentration of 5 mg/dl. six samples are taken from this solution and the following concentrations are recorded: (5.32, 4.88, 5.10, 4.73, 5.15, 4.75) mg/dl. these six measurements are assumed to be an srs of all possible measurements from solution. they are also assumed to have a standard deviation of 0.2, a normal distributin, and a mean concentration equal to the true concentration of the solution. carry out a significance test to determine whether these six measurements provide reliable evidence that the true concentration of the solution is actually not 5 mg/dl.