Atomic Number and Mass Number

• What is the structure of an atom?

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

  The number of subatomic particles can be calculated from the atom's atomic number and mass number.
• What is the atomic number of an element?

  • The atomic number is the number of protons in the nucleus of an atom.
  • Also called the proton number.
• What does it mean that all atoms of a given element have the same number of protons?

  It means that atoms of different elements have different numbers of protons.
• What is the relationship between protons and electrons in an atom?

  An atom contains equal numbers of protons and electrons.
• Why do atoms have no overall electrical charge?

  Because protons and electrons have equal and opposite charges.
• What is the atomic number of sodium?

  The atomic number of sodium is 11.
• How many protons and electrons does a sodium atom have?

  A sodium atom has 11 protons and 11 electrons.
• What is the mass number of an atom?

  The mass number is the total number of protons and neutrons in an atom.
• Can atoms of different elements have the same mass number?

  Yes, atoms of different elements can have the same mass number.
• How do you calculate the number of neutrons in an atom?

  Number of neutrons = mass number - atomic number.
• If the atomic number of a sodium atom is 11 and its mass number is 23, how many neutrons does it contain?

  It contains 12 neutrons.
• What is the process to calculate the numbers of subatomic particles in an atom?

  1. Number of protons = atomic number
  2. Number of electrons = atomic number
  3. Number of neutrons = mass number - atomic number