hi, when is whatsapp available for ipad?

WhatsApp is a third-party App. The WhatsApp developers have not released an App compatible with iPad - the available App being currently limited to iPhone.

Whilst the App is not available for iPad - you should be able to access the service using a web browser:

https://web.whatsapp.com/

Whether or not WhatsApp will ever release an equivalent App for iPad is know only to its Developers.

Ask WhatsApp

it has nothing to do with Apple.