A sample of a radioactive isotope initially contains 20 x 10^10 atoms. After 16 days, 5 x 10^10 atoms remain. what is the half-life of the isotope?

A) 12 days

B) 20 days

C) 10 days

D) 16 days

E) 8 days

How does the volume of a solid change as it melts?

What is potential energy? A) the energy of change B) the energy of position or composition C) the energy of mass or volume D) the energy of motion

Lithium (atomic number - 3), Sodium (atomic number - 11) and Potassium (atomic number - 19) are in the same group in the periodic table with valence electron 1, but potassium seems to be more reactive than sodium and lithium. Why?

Which of the following molecules would have the strongest London Dispersion Force? A. F² B. Cl² C. Br² D. I²

Which of the following is not a phase change? a. melting of snow B. evaporation of water from the ocean C. condensation of water vapor to form clouds D. hydrogen and oxygen gas combining to form water vapor

How many grams of zinc metal will react completely with 8.2 liters of 3.5 M HCl? Show all of the work needed to solve this problem. Zn (s) + 2 HCl (aq) ZnCl2 (aq) + H2 (g)

The notation for the nuclide 13755Cs gives information about (1) mass number, only (2) atomic number. only (3) both mass number and atomic number (4) neither mass number nor atomic number

Which is an example of pure chemistry

When making broccoli cream soup, the broccoli and aromatics should be A. sweated. B. puréed. C. simmered. D. burned.

Plants absorb light energy and store that energy in the form of what? A water B carbon dioxide C sugar D oxygen