atoms and isotopes

• What is the approximate radius of an atom?

  $1 \times 10^{-10} \text{ m}$
• Why is the stated radius of an atom an approximate figure?

  Some atoms are larger than others
• What is the central region of an atom called?

  The nucleus
• How does the radius of the nucleus compare to the radius of the atom?

  Less than 1/1000th the radius
• Where is almost all the mass of the atom concentrated?

  In the nucleus
• What are the two particles found in the nucleus?

  Protons and neutrons
• What is the charge of a proton?

  Positive
• What is the charge of a neutron?

  No charge (neutral)
• What is the overall charge of the nucleus?

  Positive
• What particle surrounds the nucleus?

  Electrons
• What is the charge of an electron?

  Negative
• Where are electrons found?

  In energy levels
• How does the energy level further from the nucleus compare to those closer?

  It is at a higher energy
• What determines the energy of an electron energy level?

  Distance from the nucleus
• How can electrons change energy levels?

  By gaining or losing energy
• What happens when an atom absorbs electromagnetic radiation?

  An electron moves to a higher energy level
• What happens when an atom emits electromagnetic radiation?

  An electron returns to a lower energy level
• What is the overall effect of absorbing and emitting electromagnetic radiation on electrons?

  They change energy levels
• What form of energy is associated with electron transitions between energy levels?

  Electromagnetic radiation
• How do electrons transition to a higher energy level?

  By absorbing electromagnetic radiation
• How do electrons transition to a lower energy level?

  By emitting electromagnetic radiation