The half-life of the radioactive isotope silver-104 is 30 minutes. After how many minutes will about 20 grams of a 40-gram sample of the silver-104 isotope remain? Select one:
a. 0
b. 60
c. 90
d. 30

Zoe is investigating the composition of substance a, an unknown substance. using chemical processes, she analyzes substance a and determines it is composed of sodium, oxygen, and hydrogen atoms in a ratio of 1 : 1 : 1. what is substance a? a. a compound b. an element c. a heterogeneous mixture d. a homogeneous mixture

14. many depressants reduce small muscle control, making it harder for a. you to steer b. your mind to consider complex problems c. the eye to scan, focus, or stay still d. the kidneys to filter alcohol out of the bloodstream

Which element has the lowest electronegativity? calcium(ca) gallium(ga) selenium(se) bromine(br)