What Do the Slanted Arrows Mean in Orbital Energy Levels?

[Qube]

Ok, I know that the S, P, D, and F represent blocks (groups of elements) on the periodic table.

I know that the numbers represent rows on the periodic table.

But what about the arrows? What's with the business of "increasing energy"? Why are the arrows slanted?

[PLAIN]http://i.min.us/icVeTS.png

 

[Saitama]

Ok, I know that the S, P, D, and F represent blocks (groups of elements) on the periodic table.

I know that the numbers represent rows on the periodic table.

But what about the arrows? What's with the business of "increasing energy"? Why are the arrows slanted?

[PLAIN]http://i.min.us/icVeTS.png[/QUOTE]

I don't think S, P, D, and F represent blocks. They are subshells i.e azimuthal quantum number(L) and the numbers represent the energy level, i.e Principal quantum number to which the subshells belong.

For example:- 3s
Here s is the subshell which has the azimuthal quantum number "1" and "3"(principal quantum number) is the energy level.

And about the arrows, that's just a mnemonic to remember about the order of filling of orbitals. I don't why the arrows are purposely slanted. The arrows go according to increasing energy level. If you see, the arrows go according to n+L rule.
Hope that helped...!