The Periodic Table

The Periodic Table

Basic Concepts

  • The Periodic Table is a chart illustrating elements in increasing order of their atomic numbers.
  • It consists of rows called periods and columns called groups.
  • An element’s position in the table indicates its physical and chemical properties.

Atomic Structure

  • The atomic number represents the number of protons in an atom’s nucleus.
  • Atomic mass, meanwhile, is the total number of protons and neutrons.
  • Elements in the same group have the same number of electrons in their outer shell, also referred to as valence electrons.

Groups

  • Group 1 elements, the alkali metals, are highly reactive metals with 1 electron in their outer shell.
  • Group 2 are the alkaline earth metals. They have 2 electrons in their outer shell and are less reactive than Group 1.
  • Group 7 includes the halogens, non-metals that are very reactive and have 7 electrons in their outer shell.
  • Group 0 includes noble gases, chemically unreactive gases with full outer shells.

Periods

  • The number of shells of electrons around an atom’s nucleus is indicated by its period number.
  • Elements in the same period have the same number of electron shells.

Blocks

  • Elements are also categorised into blocks (s, p, d, and f blocks) based on the type of orbitals that the outermost or valence electrons occupy.

Periodic Trends

  • Moving left to right across periods, atomic size generally decreases while ionisation energy generally increases.
  • These trends reverse when moving top to bottom down groups: atomic size generally increases and ionisation energy generally decreases.

Transition Metals

  • Grouped in the middle of the Periodic Table, transition metals have similar properties like being hard and having high melting points.
  • They form coloured compounds and have variable oxidation states.

Understanding Patterns

  • Patterns in properties and reactions of elements are predicted by their position in the Periodic Table.
  • For example, the reactivity of the alkali metals increases down the group.

Misconceptions about the Periodic Table

  • Not all elements are solid at room temperature; Bromine is a liquid and the noble gases are gases.
  • The appearance of an element does not predict its properties; lead and gold look similar but have different properties.