C HAPTER 9 N UCLEAR R ADIATION 9.1 Natural Radioactivity 1

R ADIOACTIVE I SOTOPES A radioactive isotope has an unstable nucleus. emits radiation to become more stable. can be one or more of the isotopes of an element 2

N UCLEAR R ADIATION Nuclear radiation is the radiation emitted by an unstable atom. takes the form of alpha particles, neutrons, beta particles, positrons, or gamma rays. 3

T YPES OF R ADIATION Alpha (  ) particle is two protons and two neutrons. Beta (  ) particle is a high-energy electron. 0 e Positron (  +) is a positive electron. 0 e +1 Gamma ray is high-energy radiation released from a nucleus.  4

R ADIATION P ROTECTION Radiation protection requires paper and clothing for alpha particles. a lab coat or gloves for beta particles. a lead shield or a thick concrete wall for gamma rays. limiting the amount of time spent near a radioactive source. increasing the distance from the source. 5

S HIELDING FOR R ADIATION P ROTECTION 6

C HAPTER 9 N UCLEAR R ADIATION 9.2 Nuclear Reactions 7

A LPHA D ECAY When a radioactive nucleus emits an alpha particle, a new nucleus forms that has a mass number that is decreased by 4. an atomic number that is decreased by 2. 8

B ALANCING N UCLEAR E QUATIONS In a balanced nuclear equation, the sum of the mass numbers and the sum of the atomic numbers are equal for the nuclei of the reactants and the products. MASS NUMBERS Total = 251 = Cf 247 Cm + 4 He Total = 98 = 98 ATOMIC NUMBERS 9

C HANGES IN N UCLEAR P ARTICLES D UE TO R ADIATION When radiation occurs, particles are emitted from the nucleus. mass number may change. atomic number may change. 10 Copyright © 2009 by Pearson Education, Inc.

E QUATION FOR A LPHA E MISSION Write an equation for the alpha decay of Rn-222. STEP 1: Write the incomplete equation 222 Rn ?s + 4 He 86 2 STEP 2: Determine the mass number STEP 3: Determine the atomic number STEP 4: Determine the symbol of element STEP 5: Complete the equation 222 Rn + 4 He

E XAMPLES Write a balanced nuclear equation for alpha decay of 208 Po 220 Rn

B ETA E MISSION A beta particle is an electron emitted from the nucleus. forms when a neutron in the nucleus breaks down. 1 n 0 e + 1 H

W RITING A N E QUATION FOR A B ETA E MITTER STEP 1: Write an equation for the decay of 42 potassium, a beta emitter. 42 K new nucleus + 0 e STEP 2: Mass number : STEP 3: Atomic number: STEP 4: Symbol of element: STEP 5 42 K + 0 e

L EARNING C HECK Write the nuclear equation for the beta decay of 60 Co 141 Ba 15

P OSITRON E MISSION In positron emission, a proton is converted to a neutron and a positron. 1 p 1 n + 0 e the mass number of the new nucleus is the same, but the atomic number decreases by Mn 49 Cr + 0 e

EXAMPLES Write a balanced nuclear equation for the positron emission of 127 Cs 49 K 17

G AMMA R ADIATION In gamma radiation, energy is emitted from an unstable nucleus, indicated by m following the mass number. the mass number and the atomic number of the new nucleus are the same. 99m Tc 99 Tc + 0 

EXAMPLES Write a balanced nuclear equation for the gamma emission of 27m Al 19

S UMMARY OF T YPES OF R ADIATION 20

P RODUCING R ADIOACTIVE I SOTOPES Radioactive isotopes are produced when a stable nucleus is converted to a radioactive nucleus by bombarding it with a small particle. in a process called transmutation. 21 Copyright © 2009 by Pearson Education, Inc.

L EARNING C HECK What radioactive isotope is produced when a neutron bombards 59 Co? 59 Co + 1 n ? + 4 He

C HAPTER 9 N UCLEAR R ADIATION 9.3 Radiation Measurement 23 Copyright © 2009 by Pearson Education, Inc.

R ADIATION M EASUREMENT A Geiger counter detects beta and gamma radiation. uses ions produced by radiation to create an electrical current. 24 Copyright © 2009 by Pearson Education, Inc.

R ADIATION U NITS Units of radiation include Curie - measures activity as the number of atoms that decay in 1 second. rad (radiation absorbed dose) - measures the radiation absorbed by the tissues of the body. rem (radiation equivalent) - measures the biological damage caused by different types of radiation. 25

U NITS OF R ADIATION M EASUREMENT 26

E XAMPLES What is the difference between the units of mCi and rads? 27

E XPOSURE TO R ADIATION Exposure to radiation occurs from naturally occurring radioisotopes. medical and dental procedures. air travel, radon, and smoking cigarettes. 28

L EARNING C HECK A typical intravenous dose of I-125 for a thyroid diagnostic test is 100  Ci. What is this dosage in megabecquerels (MBq)? (3.7 x Bq = 1 Ci) 1) 3.7 MBq 2) 3.7 x 10 6 MBq 3) 2.7 x 10 2 MBq 29

E XAMLES The recommended dosage of iodine-131 is 4.20 µCi/kg of body weight. How many microcuries of iodine-131 are needed for a70.0 kg patient with hyperthyroidism? 30