When was the speed of light first accurately calculated?
a. when galileo and his assistants uncovered lanterns at different hills and measured the time it took to see the light.
b. when roemer used the eclipsed moons of jupiter along with earth's orbit around the sun to compare different speeds over time.
c. when the hubble space telescope took the deep field pictures and measured how long to keep the aperture open to get the image.
d. when michelson used a rotating octagonal mirror to reflect light to a mirror on a distant mountaintop, which then reflected the light back to the rotating mirror and into an eyepiece.

Which statement describes both homogeneous mixtures and heterogeneous mixtures?

What overall charge must all compounds have

The atomic radius of sodium is 186 pm and of chlorine is 100 pm. the ionic radius for na+ is 102 pm and for cl– is 181 pm. in going from na to cl in period 3, why does the atomic radius decrease while the ionic radius increases? a. the inner electrons in the sodium cation shield its valence electrons more effectively than the inner electrons in the chloride anion do. b. the inner electrons shield the valence electrons more effectively in the chlorine atom than in the chloride anion. c. the outermost electrons in chloride experience a smaller effective nuclear charge than those in the sodium cation do. d. the outermost electrons in chloride experience a larger effective nuclear charge than those in the sodium cation do. e. monatomic ions are bigger than the atoms from which they are formed.