Squaring with preceding minus

When I put =-5^2 in a cell, it gives me 25 as a result. [....] Is that the standard Excel behaviour?

It is documented intentional behavior.  See "Calculation operators and precedence in Excel".

It is prudent to use parentheses to ensure the intended interpretation: either -(5^2) or (-5)^2.  Or we can use the POWER function: -POWER(5, 2) or POWER(-5, 2).

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TMI....

Common misunderstanding:  Excel's order (unary negation before exponentiation) is "wrong" because it is done differently in math formulas.

That is like arguing that the French are "wrong" because they write "black women" as "femmes noires", putting an adjective after the noun instead of before it. ( And the French would argue that English is "wrong". :wink: )

The point is: Excel and math are different languages, and each has its own rules of syntax.

The only reason why "minus two to the power of four" (which is ambiguous in English) "obviously" seems to be -16 in math is because math has different syntax, namely: 

and the rule is: superscript expressions have higher precedence.

Arguably, math has the "nice property" that -2^4 would be equivalent to 0 - 2^4, which is not true in Excel.

OTOH, in math, we can easily write

which is interpreted as 128 (128 = 2^7).

Is Excel "wrong" because we must write 2^(4+3) instead of simply 2^4+3, adding parentheses to force a mathematical interpretation?

( Rhetorical.  Of course not! )

Bottom line: Each language has its own syntax and rules for interpretation (semantics). It is only a coincidence -- or by purposeful design -- that some languages share some syntax and semantics. That does not make one or the other language "wrong" when there are differences.