My samsung galavy tab 7.0 is dead plugged in but stilll wont turn on?

take it to a phone repair shop and have the reset done

Try a hard reset Samsung Galaxy Tab 2 7 0 I705 hard reset

Plug a new charger

Try to use other Samsung/Android Charger.

either your battery is shot as in dead or your charger is faulty
you could try to charge it using a usb lead in your computer or another usb port to see if that works , or try another charger to eliminate your lead /charger you are using

The charger has a function that restores the battery operation parameters by discharging then charging the battery a number of times. Refer to charging instructions in the pack but I think the cycle is a 3 hourly one, time to charge from a full discharge. If the charger thinks the battery is dead then it will try to recover the battery using this process. You may have left the charger on long enough to charge then also discharge the battery.
Start again and charge for the time in the instructions ONLY, if you are not sure of the time try it for an hour, then without disconnecting the charger turn the unit on and take particular note of any screen messages, if any.
You should be able to continue as normal now, but still be aware of the time you are leaving the charger connected for, as it may take some time before it returns to normal operation and stops trying to recover what it thinks is a dead battery.

Let it charge for multiple hours before turning it on.

Once you press and hold the power button, it flashes the Samsung logo, and takes around 30 seconds to a minute to show your lock screen.

Have you tried turning it on while its on the charger?

Most likely that it's faulty. Sometimes it takes awhile before it charges itself, specially it you drained. But if you left it plugged in for a day and still nothing happened then I think it's gone dead.

Try the following though and see if it helps.

1. Press and hold the power for about 10-15 seconds. or
2. Press and hold the power and the Volume up or Volume down at the same time for about 10-15 seconds.

If nothing happens then I suggest you send your tab for a repair.

Hope it helps.