Tutor profile: Maddalena D.
Why, in Ligand Field Theory, do tetrahedral molecules almost always form high spin complexes?
The splitting of tetrahedral complexes is flipped in comparison to that of octahedral ones. The dxy, dxz, and dyz have higher energy. This is because, unlike octahedral complexes, the ligands of tetrahedral complexes come in direct contact with the dxz, dxy, and dyz orbitals. Because of the direct contact, electron repulsion increases, resulting in a higher energy. DeltaE is relatively small in complexes with fewer ligands so electrons tend to move up to the higher energy level rather than pair, creating a high spin complex.
Subject: Basic Chemistry
What is the defining factor in identifying an element? What happens when you add a proton, neutron, or electron to an element?
The amount of protons in the nucleus of an atom determines what element it is. Adding or subtracting a proton changes the identity of the element. Adding a neutron creates an isotope of that element, and adding/subtracting electron(s) from an atom allows that atom to have a charge. This is the basis of chemical reactions.
Fossils reveal that Cyprus Island, in the Mediterranean Sea, was once home to a population of dwarf elephants. Analysis of DNA from a dwarf elephant that lived 10,000 years ago—around the time the Island population went extinct—confirms that the dwarf elephants of Cyprus were closely related to normal-sized elephants on the mainland. (a) How would an evolutionary biologist explain how there came to be a population of dwarf elephants on Cyprus? (b) Identify one way in which the dwarf elephants of Cyprus refute a prediction the hypothesis of special creation and support a prediction of the hypothesis of descent with modification. Explain.
(a) The dwarf elephant evolved from an aquatic animal, and overtime developed features better equipped to live on land. This took thousands of years. The animal adapted to changes in is environment and by natural selection, the fittest animals of the population lived to reproduce. (b) The dwarf elephants of Cyprus refute a special creation hypothesis because they were an ancient species that no longer exists today, which shows change over time. This is an example of descent with modification because the modern elephant is a relative of the dwarf elephant. This shows that the elephants share a common ancestor and evolved in response to changes in their environment.
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