In this lesson, we will learn:
• To recall properties of the alkali metals
• To understand the trend in properties found in the alkali metals
• To apply knowledge of electronic structure and bonding to explain the trends in group 1 properties.
• We saw earlier that the Periodic Table is arranged, left to right, by proton number and number of outer shell electrons. The number of outer shell electrons dictates the chemical properties of an element.
Therefore, it is easy to see which elements have similar properties to each other – they will be in the same column of the table as each other, the columns which we call groups.
• The alkali metals are an example of a very well-studied group of elements with clear patterns in how their properties change.
• Alkali metals have the following properties: ∘ They are relatively soft metals. ∘ They are relatively low density metals. ∘ They are have relatively low melting points compared to metals in general. ∘ They are reactive, more so than metals in general and they react vigorously with water.
- The products of this reaction are hydrogen gas and a metal hydroxide – this forms an alkaline solution, which gives the group its name.
• As you go down the group, the properties of the elements change in the following ways: ∘ The metals get softer. ∘ The melting point of the metals gets lower. ∘ The elements get denser. ∘ The alkali metals get more reactive.
• The alkali metals all have a valence of 1, and as they are metals they form ionic compounds with non-metals. In these compounds, you’ll see alkali metals with a 1+ charge.
Alkali metals: A summary
Group 1: Alkali metals
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