Group 1 – The Alkali Metals

    OCR
    GCSE

    Group 1 elements, the alkali metals, are defined by their single outer electron, which dictates their characteristic formation of +1 ions and vigorous chemical behavior. Reactivity increases down the group; candidates must explain this via the interplay of increased atomic radius, increased shielding, and the consequent reduction in nuclear attraction for the outer electron. Reactions with water, chlorine, and oxygen produce specific observable products, notably hydrogen gas and alkaline hydroxides. Assessment prioritizes the ability to predict trends, construct balanced symbol equations, and articulate the causal relationship between atomic structure and macroscopic reactivity.

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    Objectives
    4
    Exam Tips
    4
    Pitfalls
    4
    Key Terms
    5
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for stating that reactivity increases down the group due to increased atomic radius and electron shielding
    • Credit observations such as effervescence, the metal floating, moving on the surface, and the metal diminishing in size
    • Award 1 mark for the correct balanced symbol equation, specifically including state symbols (e.g., 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g))
    • Credit responses that explain the loss of the single outer electron becomes easier as electrostatic attraction from the nucleus decreases
    • Award 1 mark for identifying that the solution turns alkaline (purple/blue with Universal Indicator) due to the formation of hydroxide ions

    Example Examiner Feedback

    Real feedback patterns examiners use when marking

    • "You correctly identified the trend, but you must explain *why* using terms like 'shielding' and 'nuclear attraction'"
    • "Good observations listed, but remember that 'gas produced' is a conclusion, not an observation—use 'effervescence'"
    • "Check your state symbols: the hydroxide dissolves in the water, so it must be (aq), not (l) or (s)"
    • "Excellent prediction for Francium; ensure you justify this by explicitly referencing the trend in atomic radius"

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that reactivity increases down the group due to increased atomic radius and electron shielding
    • Credit observations such as effervescence, the metal floating, moving on the surface, and the metal diminishing in size
    • Award 1 mark for the correct balanced symbol equation, specifically including state symbols (e.g., 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g))
    • Credit responses that explain the loss of the single outer electron becomes easier as electrostatic attraction from the nucleus decreases
    • Award 1 mark for identifying that the solution turns alkaline (purple/blue with Universal Indicator) due to the formation of hydroxide ions

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When asked to 'describe' the reaction with water, list what you see (fizzing, floating), not the names of the products formed
    • 💡For 'explain' questions regarding reactivity, use the 'RSA' mnemonic: Radius increases → Shielding increases → Attraction decreases
    • 💡Ensure state symbols are precise: Group 1 metals are (s), water is (l), hydroxides are (aq), and hydrogen is (g)
    • 💡If asked to predict properties of Francium, extrapolate the trend: very low melting point, extremely explosive reaction

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Stating 'hydrogen is produced' as an observation; candidates must record visible evidence like 'fizzing' or 'effervescence'
    • Describing the metal hydroxide product as a liquid (l) rather than an aqueous solution (aq) in symbol equations
    • Attributing increased reactivity solely to 'more shells' without explicitly linking this to weaker nuclear attraction on the outer electron
    • Confusing the flame test colour of Sodium (yellow/orange) with the observation of the metal burning during the reaction with water (only Potassium typically catches fire with a lilac flame)

    Study Guide Available

    Comprehensive revision notes & examples

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    Key Terminology

    Essential terms to know

    Electronic configuration and formation of +1 cations
    Trends in reactivity and physical properties (melting point, density)
    Reactions with water, oxygen, and chlorine
    Explanations involving shielding, atomic radius, and nuclear attraction

    Likely Command Words

    How questions on this topic are typically asked

    Describe
    Explain
    Predict
    Write
    Compare

    Practical Links

    Related required practicals

    • •{"code":"PAG C1","title":"Reactions of Group 1 elements with water","relevance":"Observation of reactivity trends and alkaline nature of products"}

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