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11.4Chapter 11: Patterns in the Periodic Table

The periodic table: Group 1 — Alhussan Chemistry - Stage 9 Revision Notes & Topical Questions

5 min read 7 parts Lesson 4 of 7 2 quizzes

📚 Alhussan Chemistry - Stage 9 Hub / Topical Revision
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Lesson summary

11.4 The periodic table: Group 1 — Alkali Metals Physical Trends — Alhussan International Academy — Chemistry (Stages 7–9) notes: Give the position of Group 1, describe and explain the pattern in its melting points and use data to describe trends.Position — Group 1 is the column …

  • Boiling point
  • Compared with other metals
  • Down the group
  • Attraction
  • Secondary source
  • Conclusion

Section 1 of 7Position and general properties

Position
  • Group 1 is the column on the left of the periodic table.
  • The elements are lithium, sodium, potassium, rubidium, caesium and francium.
Metals
  • Metals like other metals, the Group 1 elements conduct electricity and are shiny when freshly cut.
  • A freshly cut surface tarnishes quickly in air.
Softness
  • Softness they are softer than most other metals and can be cut with a knife.
Uses
  • Uses lithium is used in the batteries of electric cars, and Bolivia has huge reserves of lithium in salt flats.

Section 2 of 7Physical trends down the group

MetalMelting point (°C)Boiling point (°C)Density (g/cm3)
Lithium18113300.53
Sodium988900.97
Potassium637740.86
Rubidium396881.53
Physical trends down the group
Melting point
  • Melting point it decreases from lithium at the top to caesium at the bottom.
  • Caesium melts at about 29 °C, close to room temperature on a warm day.
Boiling point
  • Boiling point it also decreases down the group.
Softness
  • Softness the metals get softer down the group.
Compared with other metals
  • Compared with other metals melting points are low compared with a typical transition metal such as iron (1538 °C).

Section 3 of 7Explaining the melting point pattern

Explaining the melting point pattern
Structure
  • Group 1 elements have giant metallic structures in which each atom loses its one outer electron to form a positive ion.
  • The electrons move around between the ions.
Down the group
  • Down the group the outer electron gets further from the nucleus and the positive ions get bigger.
Attraction
  • Attraction the electrostatic attraction between positive ions and negative electrons gets weaker.
Result
  • Result as attractions get weaker, ions leave their fixed positions more easily, so the melting point decreases.

Section 4 of 7Presenting data and drawing conclusions

Secondary source
  • Banjeet could not measure melting points himself, so he chose a trustworthy secondary source such as a reference table.
  • Evaluate a source by asking whether it is a reliable textbook or scientific database.
Table
  • Table the independent variable (the element) goes in the left column.
Bar chart
  • Bar chart it is used because the independent variable, the element, is categoric.
    • (described by words)
Conclusion
  • Conclusion from lithium at the top to caesium at the bottom, melting point decreases.
  • Quote valueslithium melts at 181 °C and rubidium at 39 °C, a fall of 142 °C.
Predicting
  • Predicting caesium should melt below rubidium, and interpolation within the data is more reliable than extrapolation beyond it.

Section 5 of 7Density

Pattern
  • Pattern overall density increases from lithium at the top to caesium at the bottom, because the atoms become heavier.
Exception
  • Exception potassium does not fit the pattern.
Floating
  • Floating lithium, sodium and potassium are less dense than water and float, whereas rubidium and caesium are denser and sink.

Section 6 of 7Key terms

TermMeaning
Alkali metala soft, reactive metal in Group 1.
Trenda pattern in data.
Metallic bondingthe attraction between positive ions and delocalised electrons.
Interpolationestimating a value within the range of data.
Categoric variablea variable described by words.
Secondary sourcea source of data you did not collect yourself.

Section 7 of 7Exam technique

1
Saying melting point increases down Group 1 — it decreases.
2
Assuming Group 1 metals are hard like iron — they are soft enough to cut with a knife.
3
Mixing up Group 1 trends with Group 7 trends — the groups show different patterns.
4
Describing the pattern without using data — quote values from the table.

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