Now try to graph the melting and boiling point trend for elements only in Group 1, the alkali metals: (Note that by selecting the "Symbol" column instead of the "Atomic #" column, the symbols will appear on the X-axis. For chart type, select "line with markers displayed at each value.")




Compare it to a graph of the melting and boiling point trends for elements in Group 17, the halogens:

What differences or similarities do you observe?

Note that hydrogen clearly does not follow the pattern of the other elements.  In fact, hydrogen (which is a gas at room temperature) is not included in the alkali metals, even though it is located in Group 1 on the periodic table.  For the metals in this group, the melting and boiling temperatures decrease with increasing atomic number. These metals enjoy rather large liquid temperature ranges.

For the halogens, just the opposite trend is observed.  These elements show increasing melting and boiling point temperatures with increasing atomic number.  The small differences between the melting and boiling temperatures for the halogens indicate that these elements have narrow temperature ranges for their liquid states.

What other properties of elements have recognizable periodic trends?

Challenge your students to try graphing some of the other data provided in the Chem Data set to see if they can identify other periodic trends.

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