Of the first 103 elements, how many have just ine letter in their symbol

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

The peak wavelength for the blackbody curve of a star is in the uv range. assuming the radiation from this star can reach earth, would you be able to see it?

You wish to prepare a buffer consisting of acetic acid and sodium acetate with a total acetic acetate plus acetate concentration of 250 mm and a ph of 5. what concentrations of acetic acid and sodium acetate should you use