In an electrically neutral atom, the number of protons equals the number of neutrons.
protons equals the number of electrons.
neutrons equals the number of electrons.

A. Protons equals the number of neutrons
B. Protons equal the number of electrons
C. Neutrons equals the number of electrons

B

Avariable that is not being directly tested during an experiment should be

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.

State one important difference between a physical change and a chemical change?