According to the bohr model of an atom, what happens when an electron moves from the second energy level to the third energy level and then back to the second energy level? energy is absorbed and then stored in the atom. energy is released and then absorbed to form an absorption line. energy is absorbed and then released to form an emission line. energy is released from the atom, and the outer level is weakened.

The allotropes of carbon include a variety of structures that include three-dimensional tetrahedral lattices, planes of hexagonal rings, cylindrical tubes of hexagonal rings, and spheres of five- and six-membered rings. similar shapes of network covalent atomic solids are possible with carbon nitride, boron, and pure silicon (e.g., silicene is a graphene-like allotrope of pure silicon). in contrast, silicates exist as either highly ordered or amorphous (more random) three-dimensional lattices. what could explain why there are there no naturally occurring sheets, stacked sheets, cylindrical tubes, or spheres of network covalent atomic solids composed of silicon and oxygen (sio2)? would pure silicate structures make good lubricants or good electrical conductors?