K-39

Q16. Find out a little more about isotopes which Mr. Khan only mentions in the first video.

Specifically, explain what makes an isotope unstable and what an "unstable" isotope might

do.

8.

Q17. What are the elements for these abbreviations: Na, K, F, Cu, Cr, Pb, Ag, Cl, Au, Mg,

Mn, S, Ca?

Q18. What are "valence electrons" and how do they affect the behavior of the atom?

Q19. How many protons does iron (Fe) have?

Q20. How many neutrons does a stable isotope of iron (Fe) have?