Atomic Structure

Label the atomic structure?

Describe the force that holds the nucleus and electrons together?

Strong nuclear force holds the nucleus together and electrostatic force holds the electron in its orbit

What are nucleons?

Nucleons are the collection of protons and neutrons

What is technetium also used in?

nuclear medicine

What is the mass number?

-        Mass number of an element is the number of protons and neutrons in the nucleus

What is the electrostatic force also known as?

electrostatic interaction

What is the atomic number?

 number of protons in the nucleus

What is the proton number and what does it determine?

Proton number determines the characteristics of the element

What is the symbol for the atomic mass unit?

u

What is Bhor’s model?

-        Was thought electrons moved around the nucleus on fixed, circular orbits known as shells (K, L, M, N) - like plants orbiting the sun

-        Bhor’s model has been superseded

What are valence electrons?

Valence electrons are those in the most outermost shell or energy level

What is the electron cloud model?

Nucleus is surrounded by orbitals where electrons are most likely to be

What is the electron binding energy?

Energy required to overcome the positive force of the nucleus and remove the electron from its orbit

Why is the electron binding energy important?

-        How characteristic X-rays are produced

-        Shielding (in terms of x-rays) - high atomic number materials (such as lead) absorb X-ray photons as its energy is transferred in the inner shell electron

-        Dense electrons more likely to pull towards the nucleus and be absorbed

What does increased atomic number mean for the electron binding energy?

Increased atomic number = increased electron binding energy

What is the keV?

the energy it takes to knock out an inner shell electron

What are the features of atomic emissions?

Characteristic X-ray photons Produced in the X-ray tube (alongside Bremsstrahlung)

What are the features of nuclear emissions?

• Gamma photons 

• Alpha particles

• Beta particles

• Used in nuclear medicine

What is an isotope?

An isotope of an element has the same number of protons (Z) but a different number of neutrons

What is a radioisotope?

Radioisotope is a radioactive isotope with an unstable nucleus

What is radioactive decay?

Atoms which are unstable, emit excess particles and energy in the form of radiation

What is an alpha particle?

a positively charged subatomic particle made of two protons and two neutrons bound together

What are beta particles?

A beta particle is a high-energy, high-speed electron ejected from an atomic nucleus during a process called beta decay

What are gamma particles?

a packet of pure, high-energy electromagnetic radiation (a photon) emitted by the nucleus of an unstable atom

Why do alpha and beta particles have high LET?

• Alpha and beta particles ‘give up’ their energy quickly = High LET

Why are alpha particles used therapeutically instead of radiographically?

• Alpha and beta particles do not travel far = would not exit the body, therefore not detected by equipment 

• High radiation dose to the patient

Why are gamma photons useful for diagnostic imaging?

• Gamma photons of sufficient energy pass through tissue, and therefore, can be detected by the gamma camera - these are useful for diagnostic imaging

Why are alpha and beta particles more ionising?

Alpha and beta pass less tissue and are more ionising

Why are gamma particles less ionising?

• pass through longer particles and move through the body more

  • Less ionising

What are alpha, beta and gamma particles stopped by?

Alpha particles stopped by paper

Beta stopped by aluminium

Gamma particles stopped by lead 

When are characteristic x-rays produced?

• Characteristic X-rays are produced when high speed electrons collide and eject inner shell electrons (from atoms within the target anode), causing outer shell electrons to drop down and emit energy

• the electron binding energy is the energy required to remove the electron from its inner orbit

Why are high Z/Atomic number electrons used for shielding?

• High Z materials have high electron binding energies, meaning materials such as lead attenuate X-ray photons and can be used for shielding