Chemistry Chapter 25 (Nuclear Radiation)

Too few neutrons is what transformation?

1. Electron Capture: When a proton and electron become a neutron to help make it stable Ex: 59/28 Ni + 0/-1e =59/27 Co 2. Positron Emission: A proton changes to a neutron and a positron is let out. (p=e +n) *atomic number decrease by one and number of neutrons increase by 1 but mass number stay same

How many natural unstable and stable isotopes are there?

1500 unstable and 264 stable isotopes.

Alpha Particle

2 protons and 2 neutrons Helium particle

Too many protons AND neutrons is what transformation?

All nuclei that have an atomic number greater than 83 are radioactive because there are too many neutrons and protons. Therefore, alpha radiation comes into play. When alpha decay happens and alpha particles are emitted, the mass number decreases by 4 and atomic number by 2.

What are the 3 types of radiation?

Alpha, beta, gamma

Nuclear Force

Attractive force that acts between all nuclear particles that are extremely close together, such as neutrons and protons.

Too many neutrons is what transformation?

Beta Emission this takes away the neutrons and turns it into a proton that stays and an electron that leaves

Alpha radiation (characteristics and process)

Characteristics: -Consists of alpha particles (helium nuclei) -charge is 2+ -mass is 4 -Common source: Radium-226 -Not very penetrating Process: during an alpha radiation, an alpha particle is ejected and therefore, there is a new element that lost 2 protons and 4 neutrons and protons added together. ex: 252/92 Es-----> 4/2He +248/97 Bk

Beta Particle

Characteristics: -Electrons (small mass) -Charge: 1- -Common source: Carbon-14 -Moderate penetrating power (can pass through paper but not by wood) Process: Neutron turns into a proton and electron and proton stays in nucleus while the electron is ejected. -Mass number stays the same, but atomic number goes up by one ex: 3/1H----> 0/-1B +3/2 He

Transmutations

Conversion of atom of one element into an atom of another element Can be radioactive decay with alpha beta gamma radiation or caused by bombardment of nucleus (when 2 particles collide) with alpha, protons neutrons (smaller atoms)

Transuranium Elements

Elements with atomic numbers above 92, the atomic number of uranium. all radioactive

Half-Life Function

Exponential Decay

Who discovered radioactivity?

First, Antoine Henri Becquerel discovered radioactivity by leaving a sample of uranium salts without exposure to the sun. He found out that uranium was radioactive because even though it had not been exposed to the sun, it was fogged. Then, Marie Curie and Pierre Curie showed that rays emitted by uranium caused it to fog and this showed that uranium was radioactive. The three shared the 1903 Nobel Peace Prize in Physics for discovering radioactivity.

Gamma Radiation

High energy photons Usually co-emitted with alpha or beta, if alpha or beta happens, gamma may happen too. No effect in mass # or atomic # Mass: 0 because light does not have mass Common Source: Cobalt-60 Penetrating is very high: can penetrate through body but stops at lead

Chemical Reaction v. Nuclear Reactions

In both, the atoms become more stable 1. Chemicals Reactions. -the stability is because of changes with electrons in energy levels. -rate is affected by changes in temperature (faster or slower), catalysts, etc. 2. Nuclear Reactions: -unstable isotopes become stable when changes occur within nuclei -energy released -no effect from temperature -cannot be sped up, slowed down, or stopped

Where does stability stop?

Lead (Pb)

Positron

Particle with mass of electron but positive charge

What does the stability of a nucleus depend on?

Ratio of neutrons to protons. If too low or high, unstable isotope and therefore, radioactive. All nuclei that have an atomic number greater than 83 are radioactive because there are too many neutrons and protons.

Radioactivity definition

Refers to the spontaneous emission of rays or particles from certain elements.

Band of Stability

Region of the graph in which stable nuclei are located on neutron v. proton plot

Fission

Splitting the atom Can be controlled (so energy is released more slowly, nuclear reactors are used) or uncontrolled chain reaction Discovered by Otto Hahn

Radioactive Decay/Radioactivity Process

Spontaneous process that does not require an input of energy -creates products that are different isotopes (original=parent, product=daughter) -If a product is unstable, it will also decay to create new isotopes until stable product formed.

How does the number of neutrons change as protons increase in a stable isotope?

The number of neutrons increases at a higher rate

Nuclear Radiation

The rays or particles being emitted

Half-Life

Time required for half the nuclei in a radioisotope sample to decay to products. During each half-life, half of the remaining radioactive atoms decay into atoms of a new element. -can be seconds of billions of years -the decay happens to get stable isotopes so it just keeps going until it reaches that point.

Radioisotopes

Unstable isotopes

What kind of reaction is radioactivity, or radioactive decay?

example of nuclear reaction

What does the neutron to proton ratio in a radioisotope determine?

the type of decay or transformation