* Carbon (C): The backbone of all organic molecules.

* Hydrogen (H): Found in all organic molecules, often in large quantities.

* Oxygen (O): Present in many organic molecules, including carbohydrates, lipids, and proteins.

* Nitrogen (N): A key component of proteins and nucleic acids.

* Phosphorus (P): Found in nucleic acids, phospholipids, and ATP (energy carrier).

* Sulfur (S): Present in some amino acids (cysteine and methionine) and some proteins.

These elements are often referred to as CHONPS (pronounced "chumps"). While not as abundant as the first six, other elements like calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) also play important roles in certain organic molecules and biological processes.

It's important to remember that the exact elemental composition of organic matter can vary greatly depending on the specific type of organic matter. For example, plant matter will have a different composition than animal matter, and soil organic matter will have a different composition than organic matter in a lake.