Structure of the atom

• What do atoms consist of?

  Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in shells.
• How can the numbers of subatomic particles in an atom be calculated?

  The numbers of subatomic particles can be calculated from its atomic number and mass number.
• What is the structure of the atom?

  • Central nucleus containing protons and neutrons
  • Surrounded by electrons arranged in shells
  • Nucleus contains most of the mass of the atom
• What is the radius of an atom approximately?

  The radius of an atom is about $0.1 \text{ nm} (1 \times 10^{-10} \text{ m})$.
• How does the radius of a nucleus compare to that of an atom?

  The radius of a nucleus is less than $\frac{1}{10,000}$ of the radius of an atom.
• What is the radius of a typical bacterium?

  The radius of a typical bacterium is about $1 \times 10^{-6} \text{ m}$.
• What is the radius of a human hair?

  The radius of a human hair is about $1 \times 10^{-4} \text{ m}$.
• What are the subatomic particles found in the nucleus of an atom?

  • Protons: positive charge, relative mass of 1
  • Neutrons: no charge, relative mass of 1
• What is the relative charge and mass of a proton?

  The relative charge of a proton is +1 and its relative mass is 1.
• What is the relative charge and mass of a neutron?

  The relative charge of a neutron is 0 and its relative mass is 1.
• What is the relative charge and mass of an electron?

  The relative charge of an electron is -1 and its relative mass is very small.
• Where is most of the mass of an atom concentrated?

  • Most of the mass of an atom is concentrated in its nucleus.
  • Protons and neutrons contribute to the mass.
• What is the relationship between protons and electrons in terms of charge?

  Protons and electrons have electrical charges that are equal and opposite.
• What is a key fact about protons and neutrons?

  • Protons are positive.
  • Neutrons are neutral.