When is 0 considered significant

The speed of light is around 6.706×10^8 miles per hour. what is the speed of light in units of miles per minute?

Asample of aluminum foil contains 8.60 × 1023 atoms. what is the mass of the foil?

The table compares the number of electrons in two unknown neutral atoms. comparison of electrons atom number of electrons a 10 d 11 use this information to determine the number of valence electrons in the atoms. which of the following correctly compares the stability of the two atoms? both are unreactive. both are highly reactive. a is unreactive and d is reactive. a is reactive and d is unreactive.