L.1 Atomic Mass

Question 1

What is Nuclear Fussion?

Answer 1

A nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.

Small nuclei combine to form a larger nucleus (Exothermic)

Question 2

What is Nuclear Fission?

Answer 2

Large Nuclei splits into smaller nuclei. (Exothermic)

Question 3

What is Radioactive Decay?

Answer 3

Loss of small particles from nucleus

Question 4

What are the 4 types of Radioactive Decay?

Answer 4

1. Alpha
2. Beta - and Beta +
3. Gamma
4. Electron Capture

Question 5

What is Transmutation?

Answer 5

Changing one element to another or one isotope to another.

Question 6

How is Atomic Mass Calculated?

Answer 6

Adding up the masses of all isotopes and averaging them out.

This is in units of amu = (1.66054 X 10^-27 kg)

Question 7

Define Isotope

Answer 7

An isotope is an element with a different number of neutrons but that have the same number of protons as the original element in question.

Question 8

What is Avogadro’s Number?

Answer 8

This is the number of molecules that are contained in one mole of a substance. (6.02 X 10^23)

Question 9

What is the difference between Atomic Mass and Atomic Weight?

Answer 9

Atomic mass is the number of protons and neutrons in an element, given by A.

Atomic weight is the average weight of the element in question an all of its isotopes. (weighted average).

Question 10

In relation to an element, A, N, and Z are the symbols given for what?

Where are these symbols located on the table of elements?

Answer 10

A is mass the mass number. It can be found at the bottom of the symbol for the element.

N is the number of neutrons and can be known for any element by subtracting the number of protons from the atomic mass.

Z stands for the atomic number for an element, and it is the number of protons for a given element. It can be found at the top of the symbol.

Question 11

What is Strong Nuclear force? and how does it relate to the Electromagnetic force?

Answer 11

Nuclear Strong Force is the force that the protons and neutrons feel in order to come together and form the nucleus. This force has to be stronger than the electromagnetic force between the protons, which repel each other.

Question 12

What are the four fundamental forces of nature?

Answer 12

1. Strong Force
2. Weak Force
3. Electrostatic Force
4. Gravitational Force

Question 13

What is Mass defect?

Answer 13

Mass Defect is the difference between the mass of the unbonded nucleons (protons and neutrons) and the bonded nucleons within the nucleus.

Question 14

What is Nuclear Binding Energy?

Answer 14

N.B.E. is the amount of energy that is released when the nucleons come together.

E=MC ² can be used to convert the mass defect into the amount of energy in joules. The more binding energy per nucleon released, the more stable the nucleous.

Question 15

Alpha Decay

Answer 15

Alpha Decay is the emission of an alpha particle.

Loss of mass number of 4, proton number of 2.

240. 4 236

U. —> Apha. + Th

92 2 90

Question 16

Beta Negative- Decay

Answer 16

Beta - Decay is the decay of a neutron into a proton, with an emission of an electron and an antineutrino.

A A

Element ——> Different Element + 𝛽-

Z Z + 1

Question 17

Beta Positive (+) Decay

Answer 17

Beta + Decay is the decay of a proton into a neutron. Also known as a positron emission. With an emission of a positron and a neutrino.

A A

Element ——-> Different Element + 𝛽+

Z Z - 1

Question 18

Gamma Decay

Answer 18

Gamma decay is the emission of a gamma ray, which converts a high-energy nucleus into a more stable nucleus.

A A

X *. —–> X + Ɣ

Z Z

Question 19

Electron Capture

Answer 19

Electron Capture is the absorption of an electron from the inner shell that combines with a proton in the nucleus to form a neutron.

A. A

X + electron ——> Y

Z Z - 1

Question 20

The equation for the rate of nuclear decay

Answer 20

∆n / ∆t = -λt

n = number of radioactive nuclei the have not yet decayed in a sample.

λ = Decay Constant

The solution to this equation tells us how the number of radioactive nuclei changes with time. This is known as an exponential Decay.

Question 21

What is the equation for Exponential Decay

Answer 21

N(t)= N𝑜ᵉ ^-λt

N𝑜 = number of undecayed nuclei at time t = o

λ = Decay constant = ln/T (1/2) = 0.693/T(1/2)

Question 22

How is the rate of radioactive nuclei decay related to the number of nuclei?

Answer 22

In exponential decay, the rate at which radioactive nuclei decay is proportional to the number of nuclei that remain.