The Nucleus

• Give an approximation for the radius of an atom

  1x10^-10 metres
• What are the three subatomic constituents of an atom?

  Proton, Neutron and Electron.
• Where is most of the mass of an atom concentrated?

  In the nucleus.
• Approximately what proportion of the total radius of an atom is the radius of the nucleus?

  1/10,000
• Describe the arrangement of protons, neutrons and electrons in an atom.

  Protons and neutrons are found in the atom's nucleus. Electrons are found in discrete energy levels around the nucleus.
• What type of charge does the nucleus of an atom have? Why?

  Positive charge. The nucleus contains protons and neutrons. Protons have a positive charge. Neutrons have no charge.
• Give 2 ways that an atom's electron arrangement can be changed.

  Absorbing electromagnetic radiation. Emitting electromagnetic radiation.
• Explain how an atom's electron arrangement changes when it absorbs EM radiation.

  Electrons move to higher energy levels. They move away from the nucleus.
• Explain how an atom's electron arrangement changes when it emits EM radiation.

  Electrons move to a lower energy level. They move towards the nucleus.
• How does the ratio of electrons to protons in an atom result in the atom having no overall charge?

  The number of protons is equal to the number of electrons. Protons and electrons have equal and opposite charges, so charge cancels.
• What do all forms of the same element have in common?

  The number of protons.
• What is the name given to the number of protons in an atom?

  Atomic number.
• What is an atom's mass number?

  The total number of protons and neutrons in the atom.
• What is an isotope of an atom?

  An atom of an element that has a different number of neutrons, but the same number of protons.
• What property differs between isotopes of an element?

  The mass of the atom.
• How do atoms turn into positive ions?

  They lose one or more of their outer electrons. Electrons are negatively charged, so the resultant charge of the atom is positive.
• What are the relative masses of a proton, neutron and electron?

  1 - proton

  1 - neutron

  1/1850 - electron
• What is the relative charge of a proton?

  +1
• What is the relative charge of an electron?

  -1