Atomic Structure, Isotopes and Electron Shells

• What does the nucleus of an atom contain?

  Protons and neutrons
• What is the charge of protons?

  Positive charge
• What is the charge of neutrons?

  Neutral
• What is the relative mass of protons and neutrons?

  Both have a relative mass of one
• How much smaller are electrons compared to protons or neutrons?

  About two thousand times smaller
• What is the charge of electrons?

  Negative charge
• What does each box in the periodic table represent?

  A particular element
• What is the elemental symbol for lithium?

  Li
• What does the atomic number indicate?

  Number of protons in an atom
• Why is the atomic number important for identifying an element?

  It determines which element it is
• What does the mass number represent?

  Total number of protons and neutrons
• What is the mass number of lithium?

  7
• How do you determine the number of electrons in an atom?

  It equals the number of protons
• What are isotopes?

  Atoms with the same protons, different neutrons
• What is an example of an isotope of lithium?

  Lithium-6
• How many neutrons does lithium-6 have?

  Three neutrons
• What is the mass number of lithium-8?

  Eight
• What happens to unstable isotopes?

  They decay into other elements
• What is the process called when unstable isotopes decay?

  Radioactive decay
• What do electrons in an atom occupy?

  Energy levels or shells
• What happens when an electron gains enough energy?

  It jumps to a higher energy level
• What is an excited electron?

  An electron in a higher energy level
• What provides the energy for an electron to jump levels?

  Electromagnetic radiation
• What happens after an electron falls back to a lower energy level?

  It re-emits energy as radiation
• What is ionization?

  Electrons leaving the atom completely
• What charge does an atom have after ionization?

  Positive charge
• What does ionizing radiation do?

  Knocks electrons off atoms
• What are the key components of an atom?

  • Nucleus: contains protons and neutrons
  • Protons: positively charged, mass of one
  • Neutrons: neutral, mass of one
  • Electrons: negatively charged, much smaller than protons/neutrons
• What information is found in a periodic table box?

  • Elemental symbol
  • Atomic number (number of protons)
  • Mass number (total of protons and neutrons)
• What is the relationship between protons and electrons in an atom?

  • Number of protons equals number of electrons
  • This balance keeps the atom neutral
• What are the characteristics of isotopes?

  • Same number of protons (same atomic number)
  • Different number of neutrons (different mass numbers)
  • Generally, only one or two isotopes are stable
• What happens during radioactive decay?

  • Unstable isotopes emit radiation
  • Can decay into other elements
  • Types of radiation: alpha, beta, gamma
• How do electrons behave in energy levels?

  • Arranged in shells around the nucleus
  • Can jump to higher levels when gaining energy
  • Fall back and re-emit energy as radiation
• What is the significance of ionization in atoms?

  • Occurs when an electron leaves the atom
  • Results in a positive ion
  • Ionizing radiation can cause this effect