- The image displays a timeline of atomic models from ancient Greece to the modern era, showing how scientific understanding of the atom has evolved.
- Democritus (c. 400–300 B.C.) proposed that atoms are tiny, hard, and uncuttable, with different shapes explaining the properties of elements.
- John Dalton (1803) viewed the atom as a solid, indivisible sphere that cannot be destroyed or reconstructed.
- J.J. Thomson (1897) introduced the “plum pudding” model, where electrons (negative charges) are embedded in a sphere of positive charge.
- Ernest Rutherford (1909) discovered the nucleus through his gold foil experiment, proposing that atoms have a dense, positively charged center with electrons orbiting around it.
- Niels Bohr (1913) refined Rutherford’s model by suggesting that electrons occupy specific circular orbits around the nucleus, similar to planets orbiting the sun.
- The current quantum mechanical model (1926–present) describes electrons not in fixed orbits but as existing in regions called electron clouds, where their position is defined by probability—denser areas indicate higher likelihood of finding an electron.
Parent Tip: Review the logic above to help your child master the concept of properties of atoms and the periodic table worksheet answers.
