Consider the Hertzsprung Russell diagram seen here. We can use this diagram to classify stars and determine their characteristics. The color of a star is determined by its temperature: the hottest stars are blue and the coolest are red. The Sun has a surface
temperature of 5,500°C and it appears yellow. The diagram also indicates that temperature coincides with luminosity: the hotter the
star, the higher the luminosity. You can also tell the size of each star from the graph as the larger the radius, the higher the
temperature and luminosity. Regardless of a star's position in the diagram, the energy that results in high temperatures and the stars
luminosity is generated by what process?
W
A)
nuclear fusion
B)
nuclear fission
gravitational forces of swirling gases
D)
friction generated by gravitational force

Challenge question: this question is worth 6 points. as you saw in problem 9 we can have species bound to a central metal ion. these species are called ligands. in the past we have assumed all the d orbitals in some species are degenerate; however, they often are not. sometimes the ligands bound to a central metal cation can split the d orbitals. that is, some of the d orbitals will be at a lower energy state than others. ligands that have the ability to cause this splitting are called strong field ligands, cnâ’ is an example of these. if this splitting in the d orbitals is great enough electrons will fill low lying orbitals, pairing with other electrons in a given orbital, before filling higher energy orbitals. in question 7 we had fe2+, furthermore we found that there were a certain number (non-zero) of unpaired electrons. consider now fe(cn)6 4â’: here we also have fe2+, but in this case all the electrons are paired, yielding a diamagnetic species. how can you explain this?