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.
Lungs ensure that efficient gas exchange takes place between the air and the person's blood. The lungs are a pair of lobed s â¦ tructures made up of a series of highly branched tubules called bronchioles, which end in tiny air sacs called the alveoli (the alveolar membrane is the site of gas exchange).  Lungs allow us to take in oxygen from the external air and allow us to get rid of excess carbon dioxide. alveolar = air sac   simple squamous epithelium; single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelium.