radium-226 has a half-life of 1600 years. how much of a 15.25 gram sample would remain after 3200 years.

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.

the awnser is group 12