Early ideas about atoms

• What do atoms consist of?

  An atom consists of a nucleus containing protons and neutrons, surrounded by electrons in shells.
• How can the number of subatomic particles in an atom be calculated?

  The number of subatomic particles can be calculated from the atom's atomic number and mass number.
• What are the early ideas about atoms?

  • Ideas about atoms have changed over time.
  • Scientists developed new atomic models as they gathered new experimental evidence.
  • John Dalton published his ideas in 1803, proposing that all matter is made of tiny indivisible particles called atoms.
• Who published ideas about atoms in 1803?

  John Dalton
• What did John Dalton imagine atoms to be like?

  He imagined atoms as tiny spheres that could not be divided.
• Who discovered the electron?

  J J Thomson
• What model did J J Thomson propose for the atom?

  He proposed the plum pudding model of the atom.
• How did the plum pudding model describe the atom?

  The plum pudding model described the atom as a ball of positive charge with negative electrons embedded in it.
• What experiment did Ernest Rutherford design in 1909?

  He designed an experiment to test the plum pudding model using alpha particles and thin gold foil.
• What were the results of Rutherford's alpha particle scattering experiment?

  Most alpha particles went straight through the foil, but a few were scattered in different directions.
• What model did Rutherford suggest based on his experiment?

  He suggested the nuclear model of the atom.
• What are the key features of the nuclear model of the atom?

  • The mass of an atom is concentrated at its center, the nucleus.
  • The nucleus contains protons and neutrons.
  • The nucleus is positively charged.
• What is the central part of an atom called?

  The central part of an atom is called the nucleus.
• What does the nucleus of an atom contain?

  The nucleus contains protons and neutrons.
• What is the charge of the nucleus?

  The nucleus is positively charged.