How do you determine number of valence electrons an element has

Ethanol (c2h5oh) is produced from the fermentation of sucrose in the presence of enzymes. c12h22o11(aq) + h2o(g) 4 c2h5oh(l) + 4 co2(g) determine the theoretical yield and the percent yields of ethanol if 680. g sucrose undergoes fermentation and 326.5 g ethanol is obtained. theoretical _ g _ percent %

The blackbody curve for a star name zeta is shown below. what is the peak wavelength for this star ?

Which fact represents evidence for the big bang theory?