Describe a situation or investigation of fossils in which an SEM would not be a useful tool. Explain why it would not be useful.

2.4.2 Scanning Electron Microscopy With Energy-Dispersive X-Ray Spectroscopy
SEM can offer a clear, high-resolution images of the size and surface texture of plastic-like particles, allowing researchers to discriminate MPs from interfering particles in the environment matrices (Cooper and Corcoran, 2010; Remy et al., 2015). In addition, SEM or environmental SEM equipped with EDX can determine the main atomic composition of putative plastic particles, which is useful for identifying carbon-dominant plastics from inorganic particles (Eriksen et al., 2013; Vianello et al., 2013).

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.