An infant's pulse rate is measured to be 121 ± 3 beats per minute. what is the percent uncertainty in this measurement?

The infant's pulse rate is 121 ± 3 beats per minute, so the uncertainty of the measurement would be 3 beat per minute. To change it into percent uncertainty, you need to divide it with the measure value of the pulse rate. The calculation would be: 3 beat per minute/121 beat per minute= 2.48%

all matter is made up of atoms

in any element all atoms are the same

elements in a compound are always in a constant ratio: apex

oxygen is the first element in group 16 (via) of the periodic table. the periodic table is a chart that shows how chemical elements are related to each other. the elements in group 16 are said to belong to the chalcogen family. other elements in this group include  sulfur, selenium, tellurium,  and  polonium.  the name chalcogen comes from the greek word  chalkos,  meaning "ore." the first two members of the family, oxygen and sulfur, are found in most ores.

oxygen is by far the most abundant element in the earth's crust. nearly half of all the atoms in the earth are oxygen atoms. oxygen also makes up about one-fifth of the earth's atmosphere. nearly 90 percent of the weight of the oceans is due to oxygen. in addition, oxygen is thought to be the third most abundant element in the universe and in the solar system.