How much Cu-61 (half-life about 3 hours) would remain from a 2 mg sample after 6 hours?
A. 0.125 mg
B. 0.25 mg
C. 0.5 mg
O D. 1 mg

the answer is definitely c.

a electronegativity decreases beacuse the size of nucleus is bigger.

sup bro, im dumb, but this is what i found xd

"the ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (uvr) from the sun, protecting life on earth from its potentially harmful effects. when the sky is clear, there is an inverse relationship between stratospheric ozone and solar uvr measured at the earth's surface"