Atomic and nuclear physics

• Democritus in 585 BC postulated that matter is built from small particles called atoms
• Rutherford in 1911 discovered that the atom had a central part called the nucleus
• The nucleus contains protons and neutrons which are collectively called nucleons
• The simplest atom is that of hydrogen, with a nucleus consisting of a single proton
• The atomic number (Z) is equal to the number of protons in the nucleus
• The neutron number (N) is equal to the number of neutrons in the nucleus
• The atomic mass number (A) is equal to the number of nucleons (protons + neutrons) in the nucleus, A=Z+N
• Isotopes are atoms of an element that have the same number of protons but different numbers of neutrons in their nuclei
• Natural radioactivity is the spontaneous emission of radiation by unstable nuclei
• Three types of radiation emitted by a radioactive substance are alpha (α) particles, beta (β) particles, and gamma (γ) rays
• Alpha (α)-decay results in the proton number Z of the parent nuclide reducing by 2 and its mass number A decreasing by 4
• Beta (β)-decay results in the proton number Z of the parent nuclide increasing by 1 while the mass number A remains unchanged
• Gamma (γ)-decay involves the emission of fast-moving light photons by unstable excited nuclei
• All three types of radiation (alpha, beta, gamma) can ionize matter, with alpha particles having the greatest ionization power
• The penetrating ability of radiation varies, with alpha particles having the shortest range, beta particles having a shorter range than gamma rays, and gamma rays being able to penetrate a considerable thickness of concrete
• The half-life of a radioactive element is the time during which half of the unstable radioactive nuclei disintegrate
• Every radioactive element has its own characteristic half-life, indicating the time taken for half of the sample to decay
• Radioisotopes are nuclei that do not emit radiation naturally and can be changed into radioactive elements by bombarding them with protons, neutrons, or alpha particles
• Radioisotopes can be created by bombarding stable and non-radioactive elements with protons, neutrons, or alpha particles
• Radioisotopes are used in medicine, industry, and agriculture for various purposes
• Radioactive tracers are chemical compounds containing radioisotopes used to explore metabolism in the human body, animals, or plants
• In medicine, radioactive cobalt-60 is used to cure cancerous tumors and cells
• Carbon-14 is used in carbon dating to estimate the age of dead organisms by comparing its activity in live and dead samples
• Nuclear fission is a process where a heavy nucleus splits into two smaller nuclei with the release of energy
• Nuclear fusion is a process where two light nuclei combine to form a heavier nucleus with the release of energy
• fusion reaction can be shown by the following reaction:

  (2,1)H + (3,1)H ---> (4,2)He + n + energy
• The mass number of uranium is 238, so it has 92 protons and 146 neutrons.
• We can calculate the remaining atoms using the following formula:

  N=No x 1/2(t)
• Structure of an atom

  Nucleus and electrons
• Composition of the nucleus

  Protons and neutrons
• Number of protons in a nucleus


  Distinguishes one element from the other
• Representing nuclides

  Using the symbol of proton number Z, nucleon number A, and the nuclide notation X
• Unstable nuclei


  Give out radiation to get rid of excess energy and are said to be radioactive
• Types of radiation

  Alpha, Beta, Gamma
• Radioactive emissions occur randomly over space and time
• Existence of background radiation and its sources
• Carbon dating


  To estimate the age of ancient objects
• Applications of radioisotopes

  In medical, agriculture, and industrial fields
• Atom is derived from the Greek word "otomos", meaning "indivisible"
• Atoms are composite systems containing protons, neutrons, and electrons