Is null matrix skew-symmetric My question is:
Is null matrix skew-symmetric?
I think it is true as A'=-A is trivially satisfied for a null matrix. 
Please help.

To test if a matrix is skew symmetric, you need to show that:
$$-A=A^T$$
For example in the case of $2\times 2$ matrices, you need:
$$\begin{bmatrix}-a&-b\\-c&-d\end{bmatrix}=\begin{bmatrix}a&c\\b&d\end{bmatrix}$$
When we set $a=b=c=d=0$ this is trivially satisfied.

Also this is satisfied non-trivially for example in the reals, when $-a=a,-b=c,d=-d$, say:
$$M_c=\begin{bmatrix}0&-c\\c&0\end{bmatrix}:c\in \Bbb R$$
Clearly $-M_c = \begin{bmatrix}0&c\\-c&0\end{bmatrix}$ and $M_c^T = \begin{bmatrix}0&c\\-c&0\end{bmatrix}$
