The sodium ion may be abbreviated as Na+ or as simply Na. Sodium can occur as a salt in a crystalline solid. Sodium chloride (NaCl), sodium phosphate (Na2HPO4) and sodium bicarbonate (NaHCO3) are commonly occurring salts. These salts can be dissolved in water or in juices of various foods.
A Reference Point is something you use to determine the position of an object, but the reference point has to be something that doesn't move at all. For Example: A Tree. A Reference Point is something you use to determine the position of an object, but the reference point has to be something that doesn't move at all. For Example: A Tree.
Similarly in physics or maths when we try to define a location of our object we need another point from which we will tell the distance or direction or both to pin point the location. The another point is the reference point. In physics reference is often replaced with observer. Its that case when observer locates the object by starting from himself.