Solution. 1  This species has a 2â charge on it, so it is an anion. Anions are named using the stem of the element name with the suffix -ide added. 2  Because this species has no charge, it is an atom in its elemental form. This is cobalt. 3  In this case, there is a 2+ charge on the atom, so it is a cation.
1. 2. 3. The walls of the alveoli are composed of a single layer of flattened epithelial cells, as are the walls of the capillaries, so gases need to diffuse through just two thin cells. The alveoli walls are kept moist by water diffusing from the surrounding cells.he walls of the alveoli are composed of a single layer of flattened epithelial cells, as are the walls of the capillaries, so gases need to diffuse through just two thin cells. The alveoli walls are kept moist by water diffusing from the surrounding cells.
They developed a variety of respiratory surfaces that all increase the surface area for exchange, thus allowing for larger bodies. A respiratory surface is covered with thin, moist epithelial cells that allow oxygen and carbon dioxide to exchange.Those gases can only cross cell membranes when they are dissolved in water or an aqueous solution, thus respiratory surfaces must be moist.espiratory System Principles | Back to Top. 1  Movement of an oxygen-containing medium so it contacts a moist membrane overlying blood vessels. 2  Diffusion of oxygen from the medium into the blood. 3  Transport of oxygen to the tissues and cells of the body.