Atoms reading

Who first proposed the concept of atoms as indivisible units?

• Democritus and Leucippus

• John Dalton

• J.J. Thomson

• Ernest Rutherford

What significant discovery did J.J. Thomson make that challenged the notion of indivisible atoms?

• The electron

• The neutron

• The nucleus

• The proton

Which scientist introduced quantized energy levels for electrons in atomic theory?

• Niels Bohr

• Ernest Rutherford

• John Dalton

• J.J. Thomson

Who is credited with organizing the periodic table by atomic weight and predicting undiscovered elements?

• Dmitri Mendeleev

• Henry Moseley

• Antoine Lavoisier

• Johann Döbereiner

What was Henry Moseley's contribution to the periodic table?

• Rearranging elements based on atomic numbers

• Introducing the concept of triads

• Classifying elements into metals and nonmetals

• Developing the first set of chemical symbols