Nodes that has no parent node or child node are called as Atomic values.
For example:
<book> <title>Parallel Algorithm</title> <author>Rashmi Sharma</author> <year>2008</year> <price>150.00</price> </book>
<book>
<title>Parallel Algorithm</title>
<author>Rashmi Sharma</author>
<year>2008</year>
<price>150.00</price>
</book>