Carbon-14 has a half-life of approximately 5,730 years. how many half-lives have occurred in a sample that contains 50 percent of the original amount of the parent isotope?

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?

Asample of ammonia reacts with oxygen as shown. 4nh3(g) + 5o2(g) 4no(g) + 6h2o(g) what is the limiting reactant if 4.0 g of nh3 react with 8.0 g of oxygen? o2 because it produces only 0.20 mol of no. nh3 because it produces only 0.20 mol of no. o2 because it produces two times less no than nh3. nh3 because it produces three times more no than o2.

Astring vibrates with a frequency of 10 hz. why can't a person hear the sound waves produced by the vibrating string, no matter how large the amplitude of the waves? out! this is homework and due tomorrow! you so much!