Atomic Structure

• What is the basic structure of an atom?

  An atom consists of a positively charged nucleus surrounded by negatively charged electrons.
• What composes the nucleus of an atom?

  The nucleus is composed of protons and neutrons.
• How does the radius of a nucleus compare to that of an atom?

  The radius of a nucleus is less than \(1/10000\) of the radius of an atom.
• Where is most of the mass of an atom concentrated?

  Most of the mass of an atom is concentrated in the nucleus.
• How are electrons arranged in an atom?

  Electrons are arranged at different distances from the nucleus in different energy levels.
• What happens to electron arrangement when electromagnetic radiation is absorbed?

  Electrons move further from the nucleus to a higher energy level.
• What happens to electron arrangement when electromagnetic radiation is emitted?

  Electrons move closer to the nucleus to a lower energy level.
• What is the relationship between protons and electrons in a neutral atom?

  • The number of electrons is equal to the number of protons.
  • Neutral atoms have no overall electrical charge.
• What is the atomic number of an atom?

  The atomic number is the number of protons in an atom.
• What is the mass number of an atom?

  The mass number is the total number of protons and neutrons in an atom.
• What happens to atoms when they lose one or more outer electrons?

  They turn into positive ions.
• What are isotopes?

  Isotopes are atoms of the same element that have different numbers of neutrons.
• How many stable isotopes do most elements have?

  Most elements have only one or two stable isotopes.
• What is radioactive decay?

  Radioactive decay is the process by which unstable isotopes decay into more stable forms, emitting radiation.
• What types of radiation can radioactive substances emit?

  They can emit alpha particles, beta particles, gamma rays, and neutrons.
• What is an alpha particle?

  An alpha particle is the same as a helium nucleus, consisting of two protons and two neutrons.
• How far can alpha particles penetrate materials?

  Alpha particles can only travel a few centimeters in air and are easily absorbed by a sheet of paper.
• What is the radius of an atom?

  About 1x10 metres
• What is the basic structure of an atom?

  A positively charged nucleus surrounded by negative charged electrons
• What is the radius of the nucleus compared to the radius of the atom?

  The radius of the nucleus is less than 1/10,000 of the radius of the atom
• Where is most of the mass of an atom concentrated?

  In the nucleus
• How can the electron arrangement in an atom change?

  By the absorption or emission of electromagnetic radiation, which causes the electrons to move to higher or lower energy levels
• What is the number of protons in an atom called?

  The atomic number
• What is the total number of protons and neutrons in an atom called?

  The mass number
• What happens when an atom loses one or more outer electrons?

  It turns into a positive ion
• What are atoms of the same element with different numbers of neutrons called?

  Isotopes
• What is the process called when unstable isotopes decay and emit radiation?

  Radioactive decay
• What are the three main types of ionizing radiation emitted during radioactive decay?

  Alpha, beta, and gamma radiation
• How do alpha, beta, and gamma radiation differ in their penetrating power and ionizing ability?

  Alpha has low penetrating power but is strongly ionizing, beta has moderate penetrating power and ionizing ability, and gamma has high penetrating power but is weakly ionizing
• How can beta radiation be used to monitor the thickness of sheet materials?

  Beta radiation is emitted and detected on the other side of the sheet material. If the sheet becomes thicker, more beta radiation is absorbed and the detector level decreases
• How can gamma radiation be used to sterilize medical instruments?

  Gamma radiation can be used to destroy bacteria without damaging the instruments, as it is very penetrating and long-lasting
• What is the purpose of nuclear equations in representing radioactive decay?

  Nuclear equations show the element before and after decay, as well as the type of radiation emitted, while ensuring the total charge and mass numbers are conserved
• What happens to the charge and mass of the nucleus during alpha decay?

  The charge decreases by 2 and the mass decreases by 4
• What happens to the charge of the nucleus during beta decay?

  The charge increases by 1
• How do gamma rays differ from alpha and beta radiation in terms of changing the charge and mass of the nucleus?

  Gamma rays do not change the charge or mass of the nucleus, they just release excess energy
• What is the definition of a radioactive half-life?

  The time it takes for the number of radioactive nuclei in an isotope to decrease by half, or the time it takes for the count rate or activity from a sample to decrease to half its initial level
• How does the half-life of a radioactive substance relate to the rate of radioactive decay?

  A short half-life means the activity falls quickly as the nuclei are very unstable, while a long half-life means the activity falls slowly as many nuclei don't decay for a long time
• What is the difference between radioactive contamination and irradiation?

  Contamination is when unwanted radioactive atoms get onto or into an object, while irradiation is the process of exposing an object to nuclear radiation without the object becoming radioactive
• How do the different types of radiation (alpha, beta, gamma) differ in their hazards inside and outside the body?

  Outside the body, beta and gamma are most dangerous as they can penetrate the body. Inside the body, alpha is most dangerous as it does localized damage, while gamma is least dangerous as it mainly passes through. Beta is intermediate in danger inside the body.
• What are the main sources of background radiation?

  Naturally occurring unstable isotopes, cosmic rays, and small amounts from man-made sources like nuclear fallout