Hydrometer reading

I have just started brewing my brew has been fermenting for 7 days and I have read the hydrometer and it says my beer only.has an alcohol content of 2% I put 1kg of dextrose so I thought that would mean my beer would be around 4 to 5%. Does this mean the beer is still fermenting or has something went wrong I used a brand new coopers micro brew kit

The part of the hydrometer you are looking at is the potential alcohol based on the sugars left in the wort, not the actual alcohol content. If you go to the wiki here and search for hydrometer, it will explain what readings you are looking for and how to calculate ABV based on your original gravity versus your final gravity.

While your beer has been in the fermentor for 7 days there was probably a lag time before actual active fermentation began which means the beer has been fermenting for less than 7 days and is still probably fermenting. Leave it alone for another week and then take a reading. Go to the wiki as suggested in the meantime and learn how to read and calibrate your hydrometer so when you do take a reading you know what you are doing.

+1 on what maddog said. If you want to use the alcohol scale on your hydrometer you have to take the original reading minus the final reading so lets say yours read 6% pre-fermentation and now reads 2%, that means you have the 4% ABV you were expecting.

or, you can use the temperature corrected readings directly. (OG-FG)*1.33