Most of the species that lived on Earth 100 million years ago
have become extinct

Which compound contains both ionic and covalent bonds? a) hbr b)cbr4 c)nabr d) naoh

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?

How is it possible for someone to put an ear to a wall and hear someone in the next room?     a. sound waves can travel though solids.    b. the waves travel from room to room via air.    c. there must be some air in the wall so the sound can travel through it.    d. sound waves change to electromagnetic waves and then back again.