3) Rn-222 is the most stable isotope of radon. If it takes 9.74 days for a sample of Rn-222 to decay to 17%
of its initial mass, what is the half-life of Rn-222?

Which statement best describes how atoms combine to form sodium chloride (nacl)? a. a positively charged sodium ion and a positively charged chlorine ion form an covalent bond. b. a positively charged sodium ion and a negatively charged chlorine ion form an covalent bond. c. a positively charged sodium ion and a positively charged chlorine ion form an ionic bond. d. a positively charged sodium ion and a negatively charged chlorine ion form an ionic bond.

Select the correct answer. you have a nightlight plugged into an outlet in the hallway, which uses 3.5 watts when plugged in. if the house circuit provides 120.0 volts, what is the current through this bulb?

Silica, sio2, is formed on silicon as an electrically insulating layer for microelectronic devices. silica is formed when silicon is exposed to o2 gas at an elevated temperature. at 900˚c, it takes 90 minutes for the oxygen to diffuse from the surface to form a 0.06 micron (0.06 x 10-6 m) thick layer of sio2 on