Which would have more friction: a ball rolling on ice or a ball rolling on gravel?

Which element has the lowest electronegativity? calcium(ca) gallium(ga) selenium(se) bromine(br)

The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.

What is a difference between a mixture of elements and a mixture of compounds