Fundamental particles

• What are the main components of an atom?

  Protons, neutrons, and electrons.
• What charge do protons have?

  Positive charge.
• What is the charge of neutrons?

  Zero charge.
• What is the charge of electrons?

  Negative charge.
• What does the top number in an element's notation represent?

  The mass number, which is the number of protons and neutrons in the nucleus.
• What does the bottom number in an element's notation represent?

  The atomic number, which is the number of protons.
• Why are all atoms neutral?

  Because the number of protons equals the number of electrons.
• What is an ion?

  An ion is an atom with a different number of electrons and protons.
• What is a negative ion?

  A negative ion has gained electrons, resulting in a negative charge.
• How does the charge of the O2- ion arise?

  It gains two electrons, resulting in a total charge of -2.
• What is a positive ion?

  A positive ion has lost electrons, resulting in a positive charge.
• How does sodium form a Na+ ion?

  Sodium loses one electron from its outer shell, resulting in a charge of +1.
• What are isotopes?

  Isotopes are elements with the same number of protons but different numbers of neutrons.
• How do isotopes of carbon differ?

  They have the same number of protons but different numbers of neutrons (e.g., carbon-12, carbon-13, carbon-14).
• What did John Dalton propose about atoms in 1803?

  He proposed that atoms were solid spheres.
• What model did JJ Thompson create?

  The plum pudding model, which suggested that atoms were made of positive pudding with negative electrons inside.
• What did Ernest Rutherford discover about the atom?

  He discovered the nucleus and that most of the atom is empty space.
• What experiment did Rutherford use to support his model of the atom?

  The gold leaf experiment.
• What did Niels Bohr propose about electron arrangement in atoms?

  He proposed that electrons exist in fixed energy levels or shells.
• How did Bohr's model explain the emission of radiation by atoms?

  Electrons emit radiation when they move between energy levels or shells.