How many moles of oxygen does it take to react to 15 moles of iron?

Asample of silver (with work function ? = 4.52 ev) is exposed to an ultraviolet light source (? = 200 nm), which results in the ejection of photoelectrons. what changes will be observed if: silver is replaced with copper (? = 5.10 ev) more photoelectrons ejected no photoelectrons are emitted fewer photoelectrons ejected more energetic photoelectrons (on average) less energetic photoelectrons (on average)

Which of the following elements would you expect to have the lowest ionization energy value? fluorine, lithium, neon, nitrogen

__can be defined as which velocity changes