Periodic Table & Atomic Numbers Quiz

Atomic Structure and the Periodic Table

• The concept of atomic number was discovered by Henry Moseley.
• The purpose of the Periodic Table is to organize elements in a logical and systematic order.

Atomic Number and Elements

• The atomic number of an element represents the number of protons present in the nucleus of an atom.
• The smallest particle of an element that retains the properties of the element is called an atom.

Periodic Trends and Patterns

• The repeating pattern in the Periodic Table is described as periodicity.

Isotopes and Atomic Structure

• Isotopes are atoms of the same element that have the same atomic number but differ in atomic mass due to varying numbers of neutrons.

Atomic Visualization and Charged Particles

• The instrument that allows individual atoms to be seen is the Scanning Tunneling Microscope (STM).
• A cathode ray is a stream of electrons emitted from a cathode (negatively charged electrode) in a vacuum tube.
• The particles carrying a negative charge are electrons.
• J.J. Thomson measured the effects of both magnetic and electric fields on the cathode ray to determine the charge-to-mass ratio of an electron.