  In this paper we derive a formula for the number of $N$-free elements over a
finite field $\mathbb{F}_q$ with prescribed trace, in particular trace zero, in
terms of Gaussian periods. As a consequence, we derive a simple explicit
formula for the number of primitive elements, in quartic extensions of Mersenne
prime fields, having absolute trace zero. We also give a simple formula in the
case when $Q = (q^m-1)/(q-1)$ is prime. More generally, for a positive integer
$N$ whose prime factors divide $Q$ and satisfy the so called semi-primitive
condition, we give an explicit formula for the number of $N$-free elements with
arbitrary trace. In addition we show that if all the prime factors of $q-1$
divide $m$, then the number of primitive elements in $\mathbb{F}_{q^m}$, with
prescribed non-zero trace, is uniformly distributed. Finally we explore the
related number, $P_{q, m, N}(c)$, of elements in $\mathbb{F}_{q^m}$ with
multiplicative order $N$ and having trace $c \in \mathbb{F}_q$. Let $N \mid
q^m-1$ such that $L_Q \mid N$, where $L_Q$ is the largest factor of $q^m-1$
with the same radical as that of $Q$. We show there exists an element in
$\mathbb{F}_{q^m}^*$ of (large) order $N$ with trace $0$ if and only if $m \neq
2$ and $(q,m) \neq (4,3)$. Moreover we derive an explicit formula for the
number of elements in $\mathbb{F}_{p^4}$ with the corresponding large order
$L_Q = 2(p+1)(p^2+1)$ and having absolute trace zero, where $p$ is a Mersenne
prime.
