AtomQ
 Usage
• AtomQ[expr] yields True if expr is an expression which cannot be divided into subexpressions, and yields False otherwise.
Notes
• You can use AtomQ in a recursive procedure to tell when you have reached the bottom of the tree corresponding to an expression. • AtomQ gives True for symbols, numbers, strings and other raw objects, such as sparse arrays. • AtomQ gives True for any object whose subparts cannot be accessed using functions like Map. • New in Version 1; modified in 5.
| 
