Unit 3 - Science

Alpha particle

(High energy) helium nuclei w/ 2 protons and 2 neutrons - alpha decay, stopped by paper, skin, clothing; positive

Thompson experiment - conclusions

-The cathode rays were identical for all elements so all elements contain identical electrons. (Because Thompson kept changing the filament w/ different types of metals and no matter the metal it didn't affect the electrons) -Atoms are neutral so there must be positive charge in the atom to balance the negative charge (Because the electrons were accelerated towards the anode which is positive) -Electrons are tiny so there must be other particles in the atom which account for most of the mass(he knew they were small b/c they were easy to turn)

What did Marie Curie discover?

-radioactivity, polonium(named after Poland) and radium -polonium and radium more radioactive than uranium

Element

Atoms with the same atomic number have the same chemical properties and belong to the same element.

Beta particle

High energy electron(an exited negative charge) - beta decay, stopped by wood, plastic, aluminum

Heisenberg uncertainty principle

Law of Nature that says there is a limit to how well we can know where an electron is and what path it is on.

Neutrons

Neutral; the particles of the nucleus that have no charge, biggest particle, made of an electron and a proton; almost equal mass to a proton; in the nucleus

Who discovered X-Rays?

Wilhelm Roentgen 1895

Name 4 important scientists in chronological order

Wilhelm Roentgen-discovered x-rays-type of light that can go through solid matter Henri Becquerel-pitchblende and gamma rays-used photographic plates Marie Curie-radioactivity-the nucleus is CHANGING-something NEW Irene Curie-artificial transmutation-uses polonium

Atomic mass

the average of the masses of the different isotopes. The atomic mass of Hydrogen is above 1 because sometimes it can have 1 neutron and rarely it has 2. This makes the average mass above one.

Atom

Basic unit of matter, made of small particles called protons, neutrons, and electrons.; neutral charge

Fat Man

Bomb dropped on Nagasaki; plutonium based; implosion design

Migration

Form of relocation diffusion involving permanent move to a new location.

Who discovered Natural Radioactivity/Fluorescence and gamma rays?

Henri Becquerel in 1896

How is Uranium separated from U-235 and U-238? Is it physically or chemically changed

It's separated by a centrifuge. And is physically changed

Repository

a place designated for storage

Proton symbol

p+

Nucleon

proton or a neutron. Notice that the number of nucleons stays the same during radioactive decay. This means that radioactive decay obeys the Law of Conservation of Mass.

How does a magnet affect a Cathode Ray Tube TV?

-the magnet will deflect the e- path=making them go to the wrong place -alters the picture~or change one electron beam to one color phosphor to another

What did Irene Curry discover?

Artificial transmutation (uses polonium)

Fission

During fission, the nucleus of the atom splits apart producing both energy, neutrons, and lighter elements. • The heat energy released released during fission can be harnessed by a nuclear reactor to produce electricity.

Atomic number

Every element has a specific number of protons in the nucleus called the atomic number. atomic number = number of protons Number of protons are = to number of electron (same)

Does Rutherford's quote "a fly in a cathedral" refer to mass or volume? Explain.

It's referring to the mass because the cathedral is the nucleus because it's mass is soooo big(99.95% of the atom) and the electron is the fly because it is so small in mass. So in Rutherford's experiment since when the collisions of the e- and the nucleus it bounces off.

Cathode

Negative electrode, electron gun

Electron

Negative; A subatomic particle that has a negative charge, moves quickly outside the nucleus has the smallest mass in an atom

Photoluminescent

Photoluminescence is when a material glows after being exposed to light.

Rutherford model

The atom has a small, dense, positively charged nucleus The atom is mostly empty space through which electrons travel Electrons travel around the nucleus, like planets around the sun. Some alpha particles will bounce off the nucleus and be deflected

What type of wavelengths do X-Rays have?(long?short?medium?)

They had shorter wavelengths

Immobilize

prevent from moving

pitchblende

uranium ore that contains other radioactive elements

thermonic emission

-Releasing electrons through a heated filament(very thin) -Used as source of electrons for Cathode Ray Tubes -Discovered by Thomas Edison 1875=lead to the discovery of the lightbulb -how it works: hot filament releases electrons similar to evaporation carrying energy away from your body when you sweat

How does a cathode ray tube (TV) work

-The beams of electrons are turned on and off very quickly by the signal sent from the TV station. -This allows them to build up a picture on the screen. -There are 3 colors of phosphor (red, blue and green) in a color TV and they light up when electrons collide with them. -If you sit very close to the TV you can see the individual dots of red , blue and green; as you move away from the TV they merge together forming the picture you see.(similar to pointillism)

Cathode Ray tube

-essentially an electron gun that can direct the electron using a series of charged plates. -Electrons are released by the negative cathode and accelerated toward the positive anode. -A small hole in the anode allows some electrons to pass through and they are steered by the charged plates.

Phosphor

-materials which tend to give out energy as light so they glow -still glow after the incident light is removed -used for TV/Cathode Rays

Manhattan project

-was the code name for the American led effort to develop an atomic weapon during World War II. -The controversial creation and eventual use of the atomic bomb engaged some of the world's leading scientific minds, as well as the U.S. military. -The Manhattan Project was started in response to fears that German scientists had been working on a weapon using nuclear technology since the 1930s and that Adolf Hitler was prepared to use it.

(History of the atom)

1808-John Dalton suggested that all matter was made up of tiny spheres that were bouncing around and called them atoms

(History of the atom - electron)

1898-J.J. Thomson found that atoms could eject small negative particles which he called Electrons Thomson discovered that the small particles were attracted to the + plate, which meant they had a negative charge.

History of the atom (Rutherford experiment)

1910-Ernest Rutherford fired Helium nuclei (alpha particles) at a piece of gold foil which was only a few atoms thick. He found that although most of them passed through, a small few were deflected.

Orbital

A region of space where you are most likely to find the electrons. The specific shapes of the probability clouds are called Orbitals.

How does Rutherford know that the deflections were not a result of collisions with electrons?

Because the electrons would attract too the alpha particles because they were positive which wouldn't cause it to turn the opposite direction.

When X-Rays were 1st discovered, why were they so amazing?

Because they were Invisible rays with the ability to pass through solid matter.

Industrial radiography

Both polonium and radium were more radioactive than uranium. Radium became the initial industrial gamma ray source and was used to radiograph (map) steel multiple inches thick. Industrial radiography grew tremendously as part of the Navy's shipbuilding program during the Second World War.

Nucleus

Center of an atom, The nucleus accounts for 99.95% of the atomic mass but the(VERY VERY VERY TINY). • The small volume of the nucleus makes almost all the atom empty space. (Surrounding the nucleus ~ a fast moving cloud of electrons

Trans-Uranium Elements

Elements with atomic numbers greater than 92 are called the transuranium elements. One of the first attempts at creating a transuranium element was made in 1938 in Nazi Germany by bombarding uranium with neutrons. This lead to the discovery of fission less than a year before the beginning of the Second World War.

Enrich

Enriched means the concentration of U235 been increased. The U235 isotope is enriched to 5% for nuclear fuel (from the natural state of 0.7%) and is then further enriched to make weapons grade concentrations (High-Enriched Uranium or HEU).

Radiopharmaceuticals

Nuclear medicine is a specialty that uses radioactive tracers (radiopharmaceuticals) to assess bodily functions and to diagnose and treat disease. The tracer collects in the area of your body under investigation and emits radiation. These areas show up as bright spots. The tracers are designed to have a short half-life so that they don't stay in the patients system for long.

Rutherford experiment conclusions of the atom

Observation: most alpha particles travel through the foil undetected Conclusion: the atom is mostly empty space Observation: some alpha particles are deflected by small angles Conclusion: The nucleus is positively charged as is the alpha particle Observation: occasionally an alpha particle travel straight back from the foil Conclusion: The nucleus carries most of the atom's mass

Anode

Positive plate with a hole in the middle - electrons fired @ it

Proton

Positive; With neutrons in the nucleus of the atom; almost equal mass to a neutron

Thompson model of the atom

Rutherford's experiment showed Thompson's model was WRONG Plum pudding model - particles suspended in larger particle/ scattered throughout; Alpha particles would go right through the goldfoil

Probability cloud

Scientists think in terms of where the electron will most often be and call this a Probability Cloud.

Chain reaction

The neutrons that are released from the fission of one U-235 atom can go on to collide with other atoms of U-235. If enough of these expelled neutrons cause the nuclei of other U-235 atoms to split, releasing further neutrons, a fission "chain reaction" can be achieved.

X-Ray Tube/How are x-rays generated?

Thermionic emission releases electrons (e-) from the hot filament. The cathode (-) pushes the electrons towards the attracting anode (+). This push/pull —causes the electrons to speed up toward the METAL TARGET(usually Tungsten). The collisions between the high speed electrons and the metal target cause energy to be released. This energy is released as a combination of HEAT and X-RAYS. The INTENSE amount of HEAT released during the COLLISONS requires that the TARGET METAL has a HIGH MELTING POINT and be rotated to spread out the heat.

Gamma ray

Very high energy electromagnetic radiation aka light - produced by excited nucleus shooting energy, stopped by lead, steel, concrete; goes through human bodies; in all forms of decay; neutral

Does Gamma decay happens in all forms of radioactive decay? (T or F) explain

Yes, because with any decay the nucleus is exited and need to release energy. So they shoot out their energy in the form of gamma rays.

Radioactive decay

a process where particles and energy are emitted from the nucleus of an atom. This changes the composition of the nucleus and what is emitted is called radiation.

Robert Oppenheimer

affectionately known as "Oppie," was director of the Los Alamos Laboratory and responsible for the research and design of an atomic bomb. He is often known as the "father of the atomic bomb."

Isotope

atoms of the same element with different numbers of neutrons in the nucleus Isotopes of an element have the same chemical Atomic properties but the nuclear properties can be quite mass different.

Gamma decay

happens when an excited nucleus releases energy by emitting of a γ ray, a piece of very high-energy light. An excited nucleus is indicated by an asterisk (*). γ radiation and is used in many applications including cancer treatment. For example: Cobalt-60 emits γ radiation which can be aimed at tumors to kill them.

Radioactive material

has an unstable nucleus which will decay into more stable forms by altering the ratio of protons to neutrons.

Neutron symbol

n0, n

What charge do atoms have?

neutral

Vitrification

solidifying liquid waste into solid glass or ceramic logs/glass

beta decay

the emission of an electron from a nucleus. Beta decay can be thought of as the conversion of a neutron into a proton and a β particle (high energy electron).

Alpha decay

the emission of an α particle from the nucleus and primarily occurs with high mass numbers (A>200). An alpha particle is a helium nucleus, which is 2 protons and 2 neutrons.

Little boy

the name of the FIRST atomic bomb, dropped on Hiroshima; uranium based (U-238); gun type

Mass number

the number of protons and neutrons in an atom

Contamination

the process of becoming unclean

Artificial Transmutation

the transformation of atoms of one element into atoms of another element as a result of a nuclear reaction, such as bombardment with neutrons Irene and her husband Frederic shared the prize in 1935 for their work with artificial radioactivity and the transmutation of elements. Transmutation means the changing of one element into another. Irene bombarded elements with alpha particles emitted from the polonium discovered by her parents. This resulted in the production of radioactive isotopes of elements that were usually stable (artificial radioactivity).

Fluorescence

when certain minerals glow when they absorb/exposed to UV light then reemit light instantly