No. But, you can always SHIFT+click the chart object. Then, right-click on the chart, select Format Object... | Size tab | and set the Height and Width to 100%.
If you want code to set any chart to 100%, select the chart as above. Then, turn on the macro recorder, continue with the right-click process above and at the end turn off the recorder. Excel should (the macro recorder works most of the time) give you the necessary code.