Chemistry

• What does the word 'atom' mean in Greek?

  Undivided
• What did the Ancient Greeks believe about the composition of matter?

  They believed everything was made up of tiny objects that could not be split apart.
• Who suggested that elements were made of atoms of a unique single type?

  John Dalton
• What was John Dalton's contribution to atomic theory?

  He suggested that atoms of different elements could combine to form compounds.
• What significant discovery did J.J. Thomson make in 1897?

  He discovered the electron.
• What is the plum pudding model of the atom?

  It is a model where negative electrons are embedded in a mass of positive charge.
• What did the gold foil experiment conducted by Geiger and Marsden demonstrate?

  It showed something inside the atom reflecting alpha particles.
• What conclusion did Ernest Rutherford draw from the gold foil experiment?

  He concluded there must be a tiny positive nucleus at the center of the atom.
• What did Rutherford's nuclear model of the atom include?

  The nucleus contained positively charged protons.
• How did Niels Bohr refine the atomic model in 1913?

  He proposed that electrons orbit around the nucleus in shells.
• What did James Chadwick discover in 1932?

  He discovered that the nucleus also contains uncharged neutrons.
• What causes the scientific model of the atom to change over time?

  • New discoveries that don't match the current model
  • Need for updates or complete remakes to fit new information
• What is an element?

  An element is a substance that cannot be broken down into simpler substances or compounds.
• How many known unique elements are there?

  There are over 100 known unique elements.
• What is the smallest particle of an element that can exist independently?

  An atom
• How do atoms of different elements differ?

  Atoms of different elements have different atomic numbers.
• Why are all atoms neutral?

  Because they have an equal number of positive protons and negative electrons.
• What are the symbols and mass numbers for the following elements: Beryllium, Nitrogen, and Carbon?

  • Beryllium: $^{4}Be$
  • Nitrogen: $^{14}N$
  • Carbon: $^{12}C$
• What is the nucleus of an atom?

  The nucleus is the central part of an atom that contains protons and neutrons.
• What is the Bohr model of the atom?

  The Bohr model describes electrons orbiting around the nucleus in shells.
• What is the role of electrons in an atom?

  Electrons are negatively charged particles that orbit the nucleus.
• What is the charge of protons in an atom?

  Protons have a positive charge.
• What is the charge of neutrons in an atom?

  Neutrons have no charge.