An element has two isotopes. One isotope has a percent abundance of 75.0% and a mass number of 25 amu. The second isotopes has a percent abundance of25.0% and a mass number of 28 amu. What is the average atomic mass of the element? A.27.3
B.26.5
C.258
D.25.8

Which of the following statements is false regarding aromaticity? a. the compound must be cyclic b. the compound must be fully conjugated c. the compound must be planar d. the number of electrons in the pi system must satisfy the hückel 4n+2 rule e. the compound must have a neutral charge

Asap! how do you lengthen a pattern piece? (family and consumer science, sewing)

When did stem cell research become known ? who discovered stem cell? what experiments or studies have been conducted so far?