Atoms and Molecules Basics

Atomic Structure

• Atoms consist of a nucleus made up of protons and neutrons, surrounded by electron shells where electrons reside.
• An element is defined as a substance composed of only one type of atom, such as hydrogen.
• Molecules form when two or more atoms bond together, e.g., H2O (water) consists of two hydrogen atoms and one oxygen atom.
• A chemical compound is a specific quantity of a single type of molecule.

Atomic Composition

• Atomic mass is calculated by summing the number of protons and neutrons.
• The atomic number indicates the number of protons within an atom, which determines the element's identity.
• Elements are organized in the periodic table based on increasing atomic number.

Isotopes and Atomic Variants

• Isotopes have the same atomic number but different atomic mass due to varying neutron counts.
• Isobars have different atomic numbers but the same atomic mass.
• Isotones possess different atomic numbers and atomic masses but the same number of neutrons.
• Isomers have identical atomic numbers and atomic masses but exist in different energy states.

Electron Configuration

• A neutral atom has an equal number of protons and electrons, maintaining overall charge balance.
• When an atom gains or loses electrons, it becomes ionized, taking on a positive or negative charge.
• Electron shells are designated by letters (K, L, M, N, O, P, Q) and each shell can hold a specific number of electrons:
  • K shell: 2
  • L shell: 8
  • M shell: 18
  • N shell: 32
  • O shell: 50
  • P shell: 72
  • Q shell: 98

Radiation and X-Ray Techniques

• Exposure factors in radiography include kVp (kilovolt peak), mA (milliamperes), exposure time, and source-to-image receptor distance.
• kVp influences both the quality and quantity of x-rays, with higher values resulting in increased energy and penetrability.
• mA controls the number of x-rays produced but not their energy.

Interaction of X-Rays with Matter

• Attenuation refers to the reduction of radiation intensity through scattering or absorption as it passes through matter.
• Absorption occurs when energy from the x-ray beam is taken up by the irradiated material, essential for producing radiobiological effects.
• Scattering changes the direction of photons and contributes to attenuation.

Types of Scattering

• Coherent Scattering: Occurs with low-energy x-rays (<10 keV), leading to scattered x-rays with the same energy.
• Compton Scattering: Involves an incident x-ray interacting with an outer electron, resulting in lower energy and change of direction.
• Photoelectric Effect: An x-ray interacts with an inner electron, leading to its ejection and complete absorption of the x-ray.
• Pair Production: When x-rays (energy > 1.02 MeV) interact closely with a nucleus, they can produce a positron and electron.
• Photodisintegration: Involves x-rays (energy > 10 MeV) being absorbed directly by a nucleus, emitting a nucleon.

Conclusion

• Understanding atomic structure and x-ray interactions is crucial for fields like radiology, influencing both image quality and patient safety.

Explore the fundamental concepts of atoms, elements, and molecules in this quiz. Understand the composition of elements and the role of different particles like electrons, protons, and neutrons in atom structure. Test your knowledge about chemical compounds and their formation.