GCSE Chemistry Revision "Charges on Ions"

Introduction to Ionic Compounds

• Ionic compounds are formed when metals react with non-metals.

• Ions are charged atoms; metals form positive ions while non-metals form negative ions.

Metal Ions

Positive Charges

• Examples of metal ions:

  • Sodium (Na⁺): Forms a +1 ion, located in group 1.

  • Magnesium (Mg²⁺): Forms a +2 ion, located in group 2.

  • Aluminium (Al³⁺): Forms a +3 ion, located in group 3.

• Hence, the charge on a metal ion is often the same as the group number in the periodic table

Group Correlation

• The charge on metal ions usually reflects the group number:

  • Group 1: +1 ions (e.g., Li⁺, Na⁺, K⁺)

  • Group 2: +2 ions (e.g., Be²⁺, Mg²⁺, Ca²⁺)

  • Group 3: +3 ions (e.g., Al³⁺, Ga³⁺)

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• Magnesium is in group two and forms a 2 plus ion, and aluminium is in group three and that forms a 3 plus ion. We can also see this with other metals from these groups, which I'm showing you here. Both lithium and potassium are in group one and they form 1 plus ions. Beryllium and calcium are both in group two and they form 2 plus ions, and gallium and indium are in group three and these can form 3 plus ions.

Transition Metals

• Unlike main group metals, transition metals can form several different ions:

  • Iron (Fe): Can form Fe²⁺ (iron(II)) and Fe³⁺ (iron(III)).

  • Copper (Cu): Can form Cu⁺ (copper(I)) and Cu²⁺ (copper(II)).

  • 

• iron; this can form a 2 plus ion and a 3 plus ion. Scientists call these iron(II) and iron(III)

• copper, which can form a 1 plus ion and a 2 plus ion, and again we call these copper(I) and copper(II)

Non-Metal Ions

Negative Charges

• Examples of non-metal ions:

  • Oxide ion (O²⁻): Group 6, forms a -2 ion.

  • Fluoride ion (F⁻): Group 7, forms a -1 ion.

  • 

Group Correlation

• Non-metal ions charge reflects the group number:

  • Group 6: Forms -2 ions (oxygen, sulfur as sulfide S²⁻).

  • Group 7: Forms -1 ions (fluorine, chlorine, bromine).

Complex Non-Metal Ions

• there are some non-metal ions which consist of several non-metal atoms chemically combined, here:

  

• There are a couple of non-metal ions which are different from the rest, because they're positive, thus they are positively charged non-metal ions, unlike the rest of the non-metal ions which are negative, these ions are: These ions are the hydrogen ion H⁺ and the ammonium ion NH₄⁺

  

• Exceptions: Positively charged non-metal ions:

  • Hydrogen ion (H⁺)

  • Ammonium ion (NH₄⁺)

Conclusion

• Recap: Metal ions are positive and most non-metal ions are negative, correlating with their group numbers in the periodic table.

• Upcoming content will focus on calculating the formulas of ionic compounds, such as sodium sulfate (Na₂SO₄) and calcium hydroxide (Ca(OH)₂).