SCIENCE 9 LESSON 2.1 RADIATION & HALF-LIFE

examples of radioactive materials in everyday life

smoke detectors (Americium-241), nuclear energy, Food irradiation

This man discovered and named invisible high-energy emissions as X rays in 1895

Wilhelm Roentgen

what numbers seem to favor nuclear stability?

even numbers and the "magic" numbers 2, 8, 20, 28, 50, 82, 126

Most common particles emitted by radioactive materials

alpha, beta, gamma, neutron

Types of Nuclear Radiation

alpha, beta, gamma

Electron Capture Equation and definition

basically same as beta emission except baliktad

-atomic nucleus absorbs one of its inner orbiting electrons causing a proton in the nucleus to convert into a neutron.

-emits X-rays

Transmutation

changing one element to another through radioactive decay

induced transmutation

Nucleus of an unstable isotope (radionuclide) is struck with a high velocity charged particle.

Half-life

amount of time for half of a sample of a radioactive element to decay into something else

t

elapsed time

This man accidentally discovered pitchblende emitted radiation on its own without any external energy source like sunlight.

Henri Becquerel

when does alpha decay occur?

in nuclei with Z > 83

when does beta decay occur?

nuclei with a high neutron to proton ratio

when does electron capture decay occur?

heavier elements that have a low neutron to proton ratio

what should you base the number of SF on in solving for half life?

based on what is asked

nuclear chemistry

study of the structure of atomic nuclei and the changes they undergo

Isotopes

atoms of the same element that have different numbers of neutrons

Radioisotopes

emit radiation to attain more stable atomic configurations in a process called radioactive decay

Band of Stability

the location of stable nuclei when number of protons and neutrons are plotted

Location of radioactive isotopes on band of stability

outside band of stability

At what number protons do elements become unstable?

83

Alpha Decay definition and equation

- release of 2 protons and 2 neutrons

- largest and slowest, least penetrating

- changes an element to a different element with a lower atomic mass and number

Beta Radiation definition

- Two types

- Decay of a neutron into proton and electron

- Decay of a proton into a neutron and positron

- faster than alpha particles

Beta Emission Equation

mass number stays the same, proton number increases by one

Positron Emission Equation

Mass number stays the same, proton number decreases by one

Gamma Radiation Emission Definition

- not a particle

- electromagnetic wave

- no mass no charge

- very fast

- follows other types of decay

what can stop gamma radiation

several centimeters of lead

Gamma radiation emission equation

Element -> Element + gamma ray

Natural Transmutation

➢Occurs naturally as a radioisotope decays to become more stable

Half-life formula

N(t) = No(1/2)^t/t1/2

N(t)

quantity remaining

No

Initial quantity

t1/2

half life of material

pitchblende

a uranium mineral which was found to produce a photographic image even through black paper without any external energy

These 2 scientists studied radioactive materials, specifically pitchblende

Marie and Pierre Curie

What did Marie and Pierre Curie deduce after studying pitchblende?

it must contain traces of some unknown radioactive component that was far more radioactive than uranium

when does positron decay occur?

low neutron to proton ratio

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