Science is the key of life. Ok let's not go that way :P There may be times when you need access to a periodic table when only your iDevice is nearby.
EMD PTE is the solution. With this app you can access a periodic table on your iDevice. Moreover, this app does not just let you see the elements but also gives you information of the app such as who discovered it, when it was discovered and pictures of the element.
In my opinion the app has a good UI and is really helpful. The app is free and available for all iDevices. Below are a few screenshots of the app.