GRADE 9 SCIENCE 2ND MQE

Who were the first philosophers to suggest that matter is made up of tiny, indivisible particles called “atomos”?

• Aristotle and Plato

• Leucippus and Democritus

• John Dalton and J.J. Thomson

• Ernest Rutherford and Niels Bohr

What did John Dalton compare atoms to in his Billiard Ball Model?

• Tiny solid spheres that cannot be divided
  

• Positively charged clouds with electrons inside

• Electrons moving in circular orbits

• Probable regions of electron density

How did J.J. Thomson discover the electron?

• By analyzing cathode ray experiments

• By scattering alpha particles on gold foil

• By studying neutron collisions

• By measuring atomic masses

Why was Thomson’s atomic model called the Plum Pudding (or Chocolate Chip) Model?

• Electrons were scattered like chips in dough

• Atoms looked like tiny billiard balls

• Protons circled the nucleus like planets

• Electrons were arranged in fixed orbits

What conclusion did Rutherford make from the Gold Foil Experiment?

• Atoms have a dense positively charged nucleus.

• Electrons are embedded inside positive matter

• Neutrons carry most of the atom’s mass

• Energy levels hold the valence electrons

Who discovered the neutrons?

• Niels Bohr

• James Chadwick

• J.J. Thomson

• Erwin Schrödinger

What idea did Bohr introduce about how electrons move around the nucleus?

• it occupies fixed orbits with specific energy levels

• It spreads evenly like raisins in bread

• It stays inside a dense nucleus

• It exists only as clouds of probability

How does Schrödinger’s Cloud Model describe the behavior of electrons?

• As moving in unpredictable but probable regions

• As revolving in neat circular paths

• As being stuck inside the nucleus

• As balancing protons and neutrons

Which subatomic particle carries a positive charge?

• Proton

• Neutron

• Electron

• Photon

When does an electron reach an “excited state”?

• When it absorbs energy and jumps to a higher level

• When it falls back to its ground state

• When it is inside the nucleus

• When protons outnumber neutrons