The Atom

• What is all matter made up of?

  Atoms
• What is an atom?

  Smallest part of an element that can react
• What are the three subatomic particles?

  Protons, neutrons, and electrons
• What are subatomic particles?

  Particles that make up an atom
• Where is most of the mass of an atom found?

  In the nucleus
• What does the nucleus of an atom contain?

  Protons and neutrons
• What is the charge of the nucleus of an atom?

  Positively charged
• What orbits the nucleus of an atom?

  Electrons
• What is the mass of electrons compared to protons?

  Almost no mass
• What is the charge of electrons?

  Negatively charged
• What are the relative masses and charges of protons, neutrons, and electrons?

  • Proton: Mass = 1, Charge = +1
  • Neutron: Mass = 1, Charge = 0
  • Electron: Mass = 1/1836, Charge = -1
• What do nuclear symbols include?

  Atomic number and mass number
• What does the atomic number represent?

  Number of protons in an element
• What letter denotes the atomic number?

  Z
• What does the mass number represent?

  Number of protons and neutrons
• What letter denotes the mass number?

  A
• Why do atoms have no overall charge?

  Protons equal electrons in number
• What is an ion?

  A charged particle
• What are positively charged ions called?

  Cations
• How do metals typically form ions?

  By losing electrons
• What are negatively charged ions called?

  Anions
• How do non-metals typically form ions?

  By gaining electrons
• What happens to magnesium when it loses 2 electrons?

  It becomes a Mg$^{2+}$ ion
• What happens to chlorine when it gains an electron?

  It becomes a Cl$^{-}$ ion
• What is an isotope?

  Same element with different neutrons
• What do different isotopes of the same element have?

  Different mass numbers
• What do isotopes of the same element have in common?

  Identical chemical characteristics
• How do isotopes differ physically?

  Heavier isotopes have higher melting points
• How many protons and neutrons does Carbon-12 contain?

  6 protons and 6 neutrons
• How many protons and neutrons does Carbon-14 contain?

  6 protons and 8 neutrons
• What were the early atomic models proposed by Dalton and Thomson?

  • Dalton: Atoms as solid spheres
  • Thomson: Plum pudding model with electrons
• Who introduced atomic theory into chemistry?

  John Dalton
• What did J.J. Thomson prove about atoms?

  Electrons must be present in atoms
• What experiment did Rutherford conduct in 1909?

  Gold foil experiment
• What did Rutherford's gold foil experiment suggest?

  Atoms are mostly empty space
• How did Rutherford's findings conflict with Thomson's model?

  Alpha particles passed through gold foil
• What is the nuclear model of the atom?

  Atom with a tiny nucleus and electrons
• Who proposed the nuclear model of the atom?

  Ernest Rutherford
• What are the key features of Bohr's model of the atom?

  • Electrons in fixed orbits (shells)
  • Each shell has fixed energy
  • Energy is emitted or absorbed when moving shells
• What did Bohr suggest about electron movement?

  Electrons exist in fixed orbits