Comprehensive Atomic Structure, Nuclear Reactions, and Radiation Laws

Atom

the smallest particle of an element that retains the chemical properties of that element

Nucleus

center of atom, made up of protons and neutrons

Electrons

surrounds nucleus, made up of negatively charged particles

Properties of electrons

1. present in all atoms and elements 2. mass and charge never change 3. electrons have a large charge to mass ratio 4. electrons have a mass of 9.109 x 10 -31 kg

Atomic Number

Number that uniquely identifies an element

Isotopes

atoms of the same element that have different masses

How are isotopes alike?

same atomic number

How are isotopes different?

Different number of neutrons

Mass number of an isotope

total number of protons and neutrons that make up the nucleus

Mole

amount of substance that contains as many particles as there are atoms in exactly 12g of carbon-12

Abbreviation for mole

mol

Particles in one mole

6.022 x 10 23

Avogadro's number

the name given to the number of particles in a mole

Molar mass of an element

numerically equal to the atomic mass of the element in atomic mass units (g/mol)

Conversion from grams to moles

multiply grams by moles then divide by atomic mass

Conversion from grams to number of atoms

divide by molar mass and multiply by avogadro's number

Nucleus of an atom

very small region in the center of an atom that contains protons and neutrons

Discovery of the atomic nucleus

Rutherford

Particles that make up the nucleus

protons and neutrons

Law of multiple proportions

When two elements form a series of compounds, they do so in a simple, whole-number ratio.

Dalton's Atomic Theory

1. All matter is composed of extremely small particles called atoms 2. Atoms of a given element are identical in size,mass and other properties; atoms of different elements differ in size,mass, and other properties 3. Atoms cannot be subdivided, created or destroyed 4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds 5. In chemical reactions, atoms are combined, separated, or rearranged

Chemical laws explained by Dalton's theory

Conservation of mass, Definite Proportions, and Multiple Proportions.

Thomson

Discovered neutrons, plum pudding model

Millikan found

Actual electric charge (-1.6*10^-19 coulombs), oil drop experiment

Rutherford discovered

Nucleus

Geiger Counter

Instruments that detect radiation by counting electric pulses carried by gas ionized by radiation.

Film Badge

Exposure of film is used to measure the approximate radiation exposure of people working with radiation.

Scintillation Counter

Instruments that convert scintillating light to an electric signal for detecting radiation.

Fission of U-235 Induction

Induced by bombarding U-235 with slow neutrons.

Chain Reaction from Fission of U-235

The nucleus splits into medium-mass nuclei that emit more neutrons, which causes the fission of other U-235 nuclei.

Control Rods

Cadmium rods that absorb neutrons and help control reactions by limiting the number of free neutrons.

Shielding

A radiation-absorbing material that decreases exposure, especially to gamma rays.

Moderator

Carbon rods that slow down fast neutrons from fission.

Fuel in Nuclear Power Plant

U-235, 3 to 5% pure, produces energy as heat which is absorbed by coolant.

Sun's Energy Production

Fusion of hydrogen nuclei into more stable helium nuclei.

Avogadro's Number

6.02*10^23.

Mol in Volume

22.4 liters.

Last Number with 1:1 Ratio

Number 20 (Ca) is the last number with a 1:1 ratio of protons to neutrons.

Last Stable Element

Number 82 (Pb) is the last stable element. Everything after is unstable.

Radioactive Elements

Elements whose nuclei are unstable.

Unstable Nucleus

Starts to give off radiation to become stable.

Radioactive Decay

The spontaneous disintegration of a nucleus, accompanied by emission of particles, electromagnetic radiation, or both.

Spontaneous Process

A process which takes place without outside intervention. It might take years or seconds to take place.

Alpha Particle

Helium nucleus, 4/2 He.

Beta Particle

0/-1 e.

Gamma Particle

Y.

Positron

0/1 e, the antiparticle of the Beta particle.

Neutron

1/0 e.

Proton

1/1 H.

Annihilation

When positrons and beta particles collide, the particle nature is changed to electromagnetic radiation.

Half-life

The time required for a reaction to reach half of its original concentration.

Main Kinds of Nuclear Reaction

Nuclear fission and fusion.

Nuclear Fission

Several heavy nuclei can be induced to undergo fission.

Important Heavy Nuclei from Fission

U-235, U-233, Pu-239.

Chain Reaction

The reaction that multiplies and is self-sustaining.

Critical Mass

The amount of fissionable material large enough to maintain a chain reaction at a constant rate.

Subcritical Mass

The mass at which the chain reaction stops after enough neutrons are lost.

Critical Mass of U-235

1 Kg.

Significant Quantity for Nuclear Weapon

25 Kg (55 pounds) of enriched uranium.

Supercritical Mass

The mass in excess of critical mass.

Natural Uranium Purity

In nature uranium is less than 0.7% pure.

Uranium Purification

It is purified using huge centrifuge machines.

Uranium Purity for Nuclear Bombs

90% pure uranium is used.

Uranium Purity for Nuclear Power Plant

About 3.5% to 5.5%.

Controlled Fission in Nuclear Reactor

Results in energy used to heat water to produce steam to run turbine generators for energy.

Containment Shell

All nuclear reactors happen in a containment shell.

Nuclear Fusion

Low mass nuclei combine to form a heavier more stable nucleus.

Energy Source of Stars

Stars get their energy from nuclear fusion.

Hydrogen Bomb

Uses nuclear fusion.