P22_021.PDF

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Chapter 22 - 22.21

21. (a) The magnitude of the force between the (positive) ions is given by

F =

4 πε 0 r 2 = k q 2

r 2

where q is the charge on either of them and r is the distance between them. We solve for the charge:

q = r F

10 − 10 m)

3 . 7

10 − 9 N

m 2 / C 2 =3 . 2

10 − 19 C .

8 . 99

10 9 N

(b) Let N be the number of electrons missing from each ion. Then, Ne = q ,or

e = 3 . 2

10 − 19 C =2 .

1 . 6

( q )( q )

k =(5 . 0

N = q

10 − 19 C