The periodicity of the properties of elements is chiefly due to the

i) numbers of electrons in the atoms of the elements

ii) distribution of electrons in the atoms of the elements

iii) numbers of neutrons in the atoms of the elements

a) i only

b) i and iii only

c) all of these

d) ii only

e) iii only

f) ii and iii only

g) none of these

h) i and ii only

If you chip a tooth, most likely you will go to the dentist to have the missing material filled in. currently the material used to fill in teeth is a polymer that is flexible when put in, yet is hardened to the strength of a tooth after irradiation with blue light at a wavelength of 461 nm. what is the energy in joules for a photon of light at this wavelength?

Answer explain why it is not possible to deduce a complete order of reactivity.

In which phase of mitosis do the spindle fibers pull the chromosomes apart to opposite sides of the cell ?