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Periodic table development and behaviour

Atomic structure and the periodic table • The periodic table

Key concepts

What you'll likely be quizzed about

  • Early attempts to order elements involved arranging them by atomic mass and recognizing repeating properties.
  • This led to groupings of similar elements.
  • A significant advancement occurred when gaps in the periodic table predicted undiscovered elements and their properties, showcasing its explanatory power.
  • The refinement continued with the understanding that atomic number, not atomic mass, provides the correct basis for sorting elements, thereby resolving earlier inconsistencies.

Flashcards

Test your knowledge with interactive flashcards

What trend in reactivity occurs in group 7 (halogens)?

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Reactivity in halogens decreases down the group as accepting electrons becomes more challenging.

Key notes

Important points to keep in mind

Atomic number determines element identity and order.

Period number equals the highest occupied electron shell.

Group number indicates valence electrons and typical ion charge.

Metals tend to lose electrons; non-metals tend to gain or share electrons.

Alkali metal reactivity increases down the group; halogen reactivity decreases.

Ionisation energy, atomic radius, and electronegativity explain various trends.

Transition metals often exhibit multiple oxidation states; predictions require caution.

Noble gases possess full valence shells and show very low reactivity.

Predicted reactions depend on valence-electron changes and available reaction partners.

Experimental conditions can influence whether a predicted reaction occurs.

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