L 1: Atomic and nuclear structure

Question 1

How are mass and energy related

Answer 1

E=MC2, interchangeable.

Question 2

Stability of the nucleus depends on

Answer 2

Neutron proton ratio
nucleon pairing
binding energy per nucleon
Most stable nuclei has even number of n & p
Least stable nuclei has odd number of n & p

Question 3

Transition of electrons in between shells

Answer 3

going to a higher shell: absorption of energy in form of photon
going to a lower shell: release of energy in form of x-rays (Auger electron)

Question 4

Electron orbits

Answer 4

K,L,M,N

inner most is K

Question 5

Number of electrons in an orbit

Answer 5

• 2n square
• n = orbit number

Number of electrones in subshells:
2(2L+1)
See the picture for solving problems

Question 6

A

Answer 6

Atomic mass number = # of protons + neutrons

Question 7

Z

Answer 7

Atomic number = # of protons
# of protons is equal as # of electrons in the atom (stable atom)

Question 8

N

Answer 8

Neutrons = A - Z

Question 9

IsotoPes

Answer 9

2 atoms have same # of protons so same Z

P=protons

Question 10

IsotoNes

Answer 10

2 atoms have same # of neutrons so same A - Z

N=neutrons

Question 11

IsobArs

Answer 11

2 atoms have same mass number so same A

A=atomic mass

Question 12

IsomErs

Answer 12

2 atoms have same neutons and protns but different Energy levels

E=energy

Question 13

1 Atomic mass unit is

Answer 13

1.66 x 10 to the power -27 kg
2.Also, 1/2 the mass of C atom

Question 14

1 Electron volt

Answer 14

1.6 x 10 to the power -19 J

Question 15

Mass of E, P , N

Answer 15

Neutron > Proton > Electron

Question 16

To remove an electron we need how much energy?

Answer 16

0.511 MeV

Question 17

To remove an proton/neutron we need how much energy?

Answer 17

931 MeV

Question 18

Forces in nature

Answer 18

1. Gravitational forces
2. Weak Nuclear forces
3. Electromagnetic forces
4. Strong nuclear forces

Order of strength: 4 > 3 > 2 > 1

Question 19

Weak nuclear forces

Answer 19

Seen in radioactive decay

Question 20

Relation between wavelength, frequency and energy

Answer 20

As the wavelength becomes shorter, frequency becomes large and so does energy.

frequency and energy are proportional. Wavelength in inversly proportion

Question 21

atomic mass between

Stable nucleus is seen

Answer 21

A between 24 -128

Question 22

Transient Equilibrium

Answer 22

T1/2 life of parent and daughter nuclei is similar
T1/2 (P) > T1/2 (d)

Question 23

Secular Equilibrium

Answer 23

T1/2 life of parent is way larger than daughter nuclei
T1/2 (P) >&raquo_space;>T1/2 (d)
years vs days

hint: Parents are very secured!

Question 24

Types of radioactive decay

Answer 24

1. Alpha decay
2. Beta +ve decay
3. Beta -ve decay
4. Electromagnetic decay

Question 25

As the atomic number increases

Answer 25

the ratio of protons and neutrons increase

Question 26

Most stable elements are

Answer 26

Z < 20 smaller elements

Question 27

Alpha Decay

Answer 27

Decay of a heavy particle with emission of alpha particle | must have kinetic energy between 5-10 MeV to emit alpha particle

Question 28

Beta -ve decay

Answer 28

* Negatron emission * 1.7 MeV energy is emitted * High n/p ratio gives B-ve decay * So neutron rich elements

Question 29

Beta +ve decay

Answer 29

* Positron emission * Energy is emitted * Low n/p ratio gives B+ve decay & Electron capture * So proton rich elements

Question 30

Electron Capture

Answer 30

* Electron is added to the nucleus of the radioactive material * so 1 proton is transformed into neutron to maintain stability of the nucleus * It produces a new substance with z-1 = atomic number + Neutrino + energy * Characteristics x-rays and or Auger electrons are produced when the empty space in the orbit is filled by the outter electron * Low n/p ratio gives B+ve decay & Electron capture * So proton rich elements

Question 31

Unit of activity

Answer 31

Curie/Bq

Question 32

1 Ci = ? Bq | curie

Answer 32

3.7 x 10 to the power 10 Bq | 1 bq = 1 dps

Question 33

t 1/2 = | It is an intrinsic, unchanging property of a radioisotope.

Answer 33

0.693 / lamda | T1/2 is independent of temp, pressure, composition

Question 34

Mean life =

Answer 34

1/lamda = 1.44 t1/2

Question 35

Activity of radioactive element / Decay Constant =

Answer 35

A= Ao x e to the power 0.693/t1/2

Question 36

Gamma emission

Answer 36

Nuclear de-excitation: The nucleus emits a gamma ray and there is no change in either A or Z

Question 37

Velocity of electromagnetic waves =

Answer 37

Velocity (c) = lamda x frequency (v)

Question 38

Energy of photon =

Answer 38

E = h x frequency (v) E = 1.24 x 10 to the power -6

Question 39

Radiation emission from the nucleus

Answer 39

* gamma rays * particles * or both

Question 40

Nuclear Fission

Answer 40

Splitting higher Z in to 2 lower Z nuclei

Question 41

Nuclear Fussion

Answer 41

* Lighter nuclei fuse to form a heavier nuclei * Large energy is produced in this process * Fusion of H nuclei forms helium = sun's energy source

Question 42

Naturally occuring Isotopes

Answer 42

* C-14 * K-40 * U-238 * Th-232 * Ra-226

Question 43

At what atomic mass does binding energy pr nucleon peak??

Answer 43

56-62 Nuclei with atomic masses 24 - 128 have high binding energy as repellent electromagnetic forces are balanced out by strong nuclear forces.

Question 44

Protons is made of?

Answer 44

* 2 up quarks * 1 down quark * gluons all these mediate to bind them together

Question 45

Internal Conversion

Answer 45

1. X-rays: * electron cascade down to lower energy unoccupied shell. * Emits x-rays with discrete energy. 2. Auger electron emmision: * A vaccancy in an inner shell is filled by an electron in the outer shell adn another outer shell electron is ejected.

Question 46

Isomeric Transition

Answer 46

Nucleus retains its stored energy and becomes meta-stable

Question 47

Decay diagrams

Answer 47

* Higher the level of element, higher its mass energy state * B-decay= arrow points down and right * B+decay/electron capture= arrow down and left * Gamma rays emmision = down arrow * meta-stable elements = have excess energy = drawn on y axis

Question 48

UV Rays

Answer 48

* UV B rays cause cancer * UV A rays cause prematuring of the skin * UV C rays are filtered out by earth's atmosphere

Question 49

Mass Defect

Answer 49

Tha actual mass of the nucleus is as such less than the individual mass of the neutron and proton.