OCR Chemistry Textbook confusion

This is to do with: The standard enthalpy change of atomisation
Definition: The s.e.c.At of an element is the enthalpy change when 1 mole of gaseous atoms are formed from the element in its standard state.

The book changes the s.e.c.At value by a factor of a half or 2 for a reason I cannot work out.

In the OCR Chemistry 2 book pg 80/81 basically states that,
"This is another enthalpy change of at. , but this time half a mole of flurine <i>molecules</i>,1/2 F2 (g), are being converted into 1 mole of flurine <i>atoms</i>,F (g). This again is an endothermic change and it is equal to half the bond enthalpy of F2.

1/2 F2 (g) ---> F (g) s.e.c.At. = 1/2(+159) = +79.5 kJ per mole"

This does not make sense according to the definition of S.E.C.At but if you consider the units kJ per mole we only use 1/2 mole to begin with.
But using this approach on the next page it says (in diagram)

CL2 (g) ----> 2Cl (g) and this is 2 times s.e.c.At.

Which makes sense if we say that we have made 2 moles of product rather that 1 as per definition. So if we divide both sides by 2 we should have the s.e.c.At according to the value given.
However this gives

1/2 CL2 (g) ---> Cl (g) .....look familiar

Apparently this should be 1/2 s.e.c.At value. This is also reiterated in SAQ 9.4. Whereas I think this should give the whole value of s.e.c.At.

The only other thing I can think of is that it is something to do with "formed from the element in its standard state".


PAul
ps it says "it is important that you know the Born-Haber cycle for NaCl so make sure you have done SAQ 9.4 and checked your answer" obviously I got the wrong answer.