When will the public key of an address used in the network? On block explorer there are some address with public key available, and some without.

(e.g. this one has public key: 

http://blockexplorer.com/address/1HBheYzvX7NDtcwVrMS7gxReNRVezYS7w2 ,

and this one doesn't:

http://blockexplorer.com/address/1111111111111111111114oLvT2)

Why is that?

Is it because one has money sent out and one doesn't?

If I understand correctly then the public key is included in the transaction out of an address, is that right?
The 1111111111111111111114oLvT2 hasn't been spent yet whereas 1HBheYzvX7NDtcwVrMS7gxReNRVezYS7w2 has.

To spend, the public key is part of the INPUT's ScriptSig:


http://en.bitcoin.it/wiki/Transactions#Explanation


So until there is a spend transaction, the public key isn't known to the network, just the Bitcoin address.

Related: Why is it impossible to derive public key from address?