Major elements in seawater
Elements present in amounts greater than 1 mg/litre are called major elements (Table 1). These elements determine the salinity of seawater. Their ratios with salinity or with each other are nearly constant. They are also known as conservative elements. Common salt (sodium chloride) is the principal ingredient of seawater that makes it salty. It exists in solution as separate hydrated sodium ions (Na+) and hydrated chloride ions (Cl-).