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Core: Describe the Group I alkali metals, lithium, sodium and potassium, as relatively soft metals with general trends down the group, limited to:
Core: Predict the properties of other elements in Group I, given information about the elements
Group I metals are commonly known as the alkali metals. These metals exhibit unique physical and chemical properties that distinguish them from other elements in the periodic table.
The alkali metals share several common features:
Important: When freshly cut with a knife, all alkali metals display a light-grey, silvery surface which quickly tarnishes and becomes dull due to rapid oxidation in air.
The physical properties of Group I metals change in a predictable pattern as we move down the group.
| Metal | Electronic Configuration | Density / g/cm3 | Melting Point / °C | Boiling Point / °C | Hardness |
|---|---|---|---|---|---|
| Lithium | 2,1 | 0.53 | 181 | 1342 | fairly soft |
| Sodium | 2,8,1 | 0.97 | 98 | 883 | soft |
| Potassium | 2,8,8,1 | 0.86* | 63 | 760 | very soft |
*Note: The density value for sodium is higher than would be expected from the general trend.
As we move down Group I, the melting points decrease:
The pattern shows that each successive element has a lower melting point than the one above it. Similarly, boiling points also decrease down the group.
As we move down Group I, the density generally increases:
Although the general trend is increasing density, this pattern is slightly obscured because sodium's density is higher than would be expected from a smooth progression.
The metals become progressively softer as we descend the group:
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