The most abudant ion of cell interior is potassium and that of outside is soddium but in active transport concept.....why theories start saying 3Na move out and 2K move in?

Dear student 

In general, the inside of a cell has a higher concentration of potassium (k+) and a lower concentr of sodium  than the extracellular fluid around it.
If sodium ions are outside of a cell, they will tend to move into the cell based on both their concentration gradient (the lower concentration of Na +  in the cell) and the voltage across the membrane (the more negative charge on the inside of the membrane).
Because k+ is  positive, the voltage across the membrane will encourage its movement into the cell, but its concentration gradient will tend to drive it out of the cell (towards the region of lower concentration). The final concentrations of potassium on the two sides of the membrane will be a balance between these opposing forces.

Hope this helps 

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