To which series will the following elements belong? 257 103 Lr , 254 99 Es , 243 95 Am

Lr 103 257 : 257 is divisible by 4 , with remainder being 1 , hence, Lr 103 257 belongs to 4 n + 1 series. Es 99 254 : 254 is divisible by 4 , with remainder being 2 , hence, Es 99 254 belongs to 4 n + 2 series. Am 95 243 : 243 is divisible by 4 , with remainder being 3 , hence, Am 95 243 belongs to 4 n + 3 series.

A sample of carbon from an ancient frame gives 7 counts of C 14 per minute per gram of carbon. If freshly cut wood gives 15 . 3 counts of C 14 per minute per gram, what is the age of the frame? (Half-life period of C 14 = 5770 years)

N = 7 count / minute N 0 = 15 . 3 count / minute N = N 0 1 2 t t 1 / 2 7 15 . 3 = 1 2 t 5770 Taking log on both sides and solving, log 7 15 . 3 = log 1 2 t 5770 log 7 - log 15 . 3 = t 5770 log 1 2 0 . 8451 - 1 . 1847 = t 5770 [ log 1 - log 2 ] - 0 . 3396 = t 5770 [ 0 - 0 . 3010 ] t = 6510 years

E M B I B E

Modern Approach to Chemical Calculations>Chapter 11 - Atomic Structure and Radioactivity>PROBLEMS>Q 34

MEDIUM

JEE Main

IMPORTANT

Earn 100

Predict the type of radioactive decay process that is likely for each of the following nuclides.

(a) ${}_{92}^{228}U$ (b) ${}_{5}^{8}B$ (c) ${}_{29}^{68}{Cu}$

50% studentsanswered this correctly

Important Questions on Atomic Structure and Radioactivity

MEDIUM

JEE Main

IMPORTANT

Modern Approach to Chemical Calculations>Chapter 11 - Atomic Structure and Radioactivity>PROBLEMS>Q 35

If

28.0 %

of a sample of

Ag

-

112

decays in

1.52 h

, what is the half-life of this isotope?

MEDIUM

JEE Main

IMPORTANT

Modern Approach to Chemical Calculations>Chapter 11 - Atomic Structure and Radioactivity>PROBLEMS>Q 36

{}_{90}^{232}{Th}

disintegrates to

{}_{y}^{x}{Pb}

by emitting six

α

- and four

β

-particles. Find

x

and

y

.

EASY

JEE Main

IMPORTANT

Modern Approach to Chemical Calculations>Chapter 11 - Atomic Structure and Radioactivity>PROBLEMS>Q 37

If Uranium (mass number $238$ and atomic number $92$ ) emits an $α$ -particle, the product has the mass number and atomic number:

(a) $236$ and $92$

(b) $234$ and $90$

(c) $238$ and $90$

(d) $236$ and $90$

HARD

JEE Main

IMPORTANT

Modern Approach to Chemical Calculations>Chapter 11 - Atomic Structure and Radioactivity>PROBLEMS>Q 38

To which series will the following elements belong?

$\begin{array}{l} 257 \\ 103 \end{array} Lr, \begin{matrix} 254 \\ 99 \end{matrix} Es, \begin{matrix} 243 \\ 95 \end{matrix} Am$

MEDIUM

JEE Main

IMPORTANT

Modern Approach to Chemical Calculations>Chapter 11 - Atomic Structure and Radioactivity>PROBLEMS>Q 39

A sample of carbon from an ancient frame gives

7

counts of

{}^{14}C

per minute per gram of carbon. If freshly cut wood gives

15.3

counts of

{}^{14}C

per minute per gram, what is the age of the frame? (Half-life period of

{}^{14}C = 5770

years)

MEDIUM

JEE Main

IMPORTANT

Modern Approach to Chemical Calculations>Chapter 11 - Atomic Structure and Radioactivity>PROBLEMS>Q 40

Calculate the number of atoms disintegrating per minute in a mass of

0.001 g

of radium which is an

α -

emitter with a half-life period of

1620

years.

HARD

JEE Main

IMPORTANT

Modern Approach to Chemical Calculations>Chapter 11 - Atomic Structure and Radioactivity>PROBLEMS>Q 41

In a sample of pitchblende, the atomic ratio is ${}^{206}{Pb} : {}^{238}U = 0.23 : 1 .$ The age of the mineral is $B \times 10^{9}$ , if the half-life of uranium is taken as $4.5 \times 10^{9}$ years. All lead originated from uranium. (Report the value of B in two significant figures.)