PLEASE HURYY What does the half-life of a radioisotope refer to?
A. The length of time the radioisotope exists as a parent element
B. Half of the total energy that will be released by a radioactive
sample
C. The length of time it takes for half of a radioactive sample to
decay
D. Half of the length of time the radioisotope remains radioactive

Which of the following elements would you expect to have the lowest ionization energy value? fluorine, lithium, neon, nitrogen

Inside a flashbulb, oxygen surrounds a thin coil of magnesium. when the flashbulb is set off, a chemical reaction takes place in which magnesium combines with oxygen to form magnesium oxide. which of the chemical equations matches the reaction above? a. mg + o2 mgo2 + energy b. 2mg + o mg2o + energy c. 2mg + o2 2mgo + energy d. mg + o mgo + energy

The biosphere of the earth is made up of what compound? organic or inorganic?