Size and mass of atoms

• what is the structure of the atom?

  Nucleus surrounded by electrons.
• What does the top number represent?

  atomic mass

  
• What does the letters mean?

  The element symbol

  
• What element is this?

  Sodium

  
• What does the bottom number represent?

  Atomic number

  
• What is the atomic number?

  The number of protons in an atom's nucleus.
• what is the mass number of an atom?

  The total number of protons and neutrons in an atom
• What is the atomic mass?

  The total mass of an atom, which is the sum of the masses of its protons, neutrons, and electrons.
• Why do atoms have no overall charge?

  Equal number of protons and electrons.
• What is the radius of an atom?

  0.1 nm (1 × 10-10 m)
• What is the radius of the nucleus of an atom?

  (1 × 10-14 m) is less than 1/10,000 of the radius of an atom
• Where is all of the mass of an atom?

  Nucleus
• What is the relative mass of a proton?


  1
• What is the relative mass of a neutron?


  1
• What is the relative mass of an electron?


  1/2000, very small
• What is the sum of the protons and neutrons in an atom called?


  Mass number
• What is the mass number of an atom?


  The mass number of an atom is the total number of protons and neutrons in its nucleus.
• What are isotopes?


  Isotopes are atoms of the same element that have different numbers of neutrons.