Give one example mechanical digestion that takes place in the mouth

The air exhaled from the lungs of a smoker has a concentration of 24 ppm co. express the concentration as a percent.

The alkali metals (group 1) consist of lithium (3), sodium (11), potassium (19), rubidium (37), cesium (55), and francium (87). they are soft, metallic solids with low densities and low melting points. based on the data shown in figure 1, how many valence electrons do alkali metals share?

Can someone me with questions 15 to 17 plz.