Less common C2.3

Key Groups in the Periodic Table

The Periodic Table is a map of the elements arranged by increasing atomic number. Knowing the location of key groups allows you to quickly deduce an element's properties, such as whether it's a reactive metal or an inert gas.

Part of the ESAT Chemistry syllabus — revision for the Engineering and Science Admissions Test (ESAT), the UAT-UK admissions test for Cambridge, Imperial, Oxford and UCL.

Key points

  • Metals are found on the left and in the centre of the table; non-metals are on the upper-right.
  • Group 1 elements are the highly reactive Alkali Metals.
  • Group 2 elements are the Alkaline Earth Metals.
  • Group 17 elements are the Halogens, which are highly reactive non-metals.
  • Group 18 elements are the Noble Gases, which are chemically inert.
  • The central d-block (Groups 3-12) contains the Transition Metals.

Diagram

Periodic table snippetOutline of the main groups with highlighted positions. Groups I - VIII
Key groups of the periodic table highlighted: Group 1 (alkali metals, left), Group 2 (alkaline earth metals, left-centre), and Group 18 (noble gases, far right) shown across all periods, illustrating their locations and organization.

Definitions

Alkali Metals
The elements in Group 1, which are soft, highly reactive metals with one electron in their outermost shell.
Alkaline Earth Metals
The elements in Group 2, which are reactive metals, but typically less so than the alkali metals.
Halogens
The elements in Group 17, which are very reactive non-metals that exist as diatomic molecules at room temperature.
Noble Gases
The elements in Group 18, which are unreactive (inert) gases due to having a full outer shell of electrons.
Transition Metals
The large block of elements between Group 2 and Group 13, known for forming coloured compounds and having multiple oxidation states.

Worked example

An unknown element is a solid at room temperature and is located in Period 4. It is more reactive than Zinc (Zn) but less reactive than Potassium (K). To which named group of elements does it most likely belong?

  1. 1

    First, locate the given elements in Period 4.

    Potassium (K) is in Group 1, the Alkali Metals.

    Zinc (Zn) is a Transition Metal in Group 12.

  2. 2

    Reactivity for metals in the same period generally decreases from left to right.

  3. 3

    The unknown element is less reactive than Potassium (Group 1), so it must be to the right of Group 1.

  4. 4

    It is more reactive than Zinc (Group 12), so it must be to the left of the main transition metal block.

  5. 5

    The group that fits this position and description is Group 2, which contains Calcium (Ca) in Period 4.

    This group is known as the Alkaline Earth Metals.

Answer: Alkaline Earth Metals

Common mistakes

  • ×Confusing the location of metals (left) and non-metals (right).
  • ×Mixing up the names of the key groups, for example, calling Group 1 the Halogens.
  • ×Forgetting that Hydrogen, although in Group 1, is a non-metal and does not share the properties of alkali metals.

No-calculator tips

  • ✓Create a mental map: Far left = very reactive metals. Far right = unreactive gases. Second from right = very reactive non-metals. Middle = typical metals.
  • ✓Use the group number as a clue to properties: Group 1 metals want to lose 1 electron, Group 17 halogens want to gain 1 electron, making them very reactive.
  • ✓Remember the 'staircase' line dividing metals and non-metals, which starts under Boron (B) and steps down and to the right.

Read this topic in the official UAT-UK ESAT guide →

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