6.1 - Atomic Structure, Isotopes & 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
• What is the mass number of lithium?

  7
• What are isotopes?

  Atoms with the same protons, different neutrons
• Which subatomic particles make up the nucleus of an atom?

  • Protons
  • Neutrons
• What is generally true about an element's isotopes?

  Only one or two are stable
• What happens to unstable isotopes?

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

  Radioactive decay
• What is an excited electron?

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

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

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

  When an electron leaves the atom
• What charge does an atom have after losing an electron?

  Positive charge
• What is a positive ion?

  An atom with more protons than electrons
• What does ionizing radiation do?

  Knocks electrons off atoms
• What are the charges of the subatomic particles?

  Electron: 1-

  Proton: 1+

  Neutron: 0
• What are the relative masses of the following subatomic particles?

  Proton: 1

  Neutron: 1
• Isotopes are atoms with the same number of protons but different number of neutrons
• Some isotopes are unstable and can decay into other elements. Decay involves emitting radiation such as alpha, beta, and gamma radiation.
• • Electrons orbit the nucleus at specific energy levels which are also called shells.
  • shells get progressively 

  further from the nucleus and increase in energy level.

  • Electrons can absorb electromagnetic radiation and jump to a higher energy level / shell. In these cases we say that the electron has become 'excited'.
  • Excited electrons can later fall back to a lower energy level, and 

  emit electromagnetic radiation in the process.

  • Electrons can also absorb enough energy to leave the atom altogether, this is known as ionisation.