user23844: I'm new to chess (around 1000), and I like to practice the Scandinavian defence. I started to check the theory related to it, and I've never seen a single source talking about this queen move after Nc3.
[FEN ""]
1.e4 d5 2.exd5 Qxd5 3.Nc3 Qe5+

I guess it's a bad one, otherwise they would mention it. But why is it a bad move? I've been playing this since I started (unconsciously) and I see no particular drawback (I just need to be careful not to make my queen stuck). 
I understand that this opening violates the rule of development, but I don't feel the late when I play it. I often find a way to harasa my opponent (maybe it's because of my low rank, it becomes more visible at high rank?). Here are 2 variants I often end up with. As you can see I develop as good as white and I have even the queenside castling (almost) ready.
When defending with bishop:
[FEN "eoui"]
1. e4 d5 2. exd5 Qxd5 3. Nc3 Qe5+ 4. Be2 Bg4

When defending with knight:
[FEN ""]
1. e4 d5 2. exd5 Qxd5 3. Nc3 Qe5+ 4. Nge2 Bf5 5. d3 Nc6


user14471: Qe5+ is not a blunder or a mistake but it is definitely inaccurate play. Qa5 (most popular line) keeps a check on 2 central squares as well as Qd8.    


Defending with bishop

Also in the second line you mentioned (Bc2) after Bg4, white has an excellent move d5! Now white has a tempo in development, space as well as development whereas black is trying to play with two pieces. Once you play the recommended Bxe2 Nxe2 the advantage for white is apparent as black scrambles to position his queen and start development when white has two pieces and a pawn out in the game.
This is why it's a bad idea to play Qe5+. It may not look like you're losing much but the advantage white has is more apparent the higher the level you play at.

user4418: 
But why it's a bad move?

You are moving your queen to a square where it is going to be attacked again soon and then you will have to move the queen for a third time. Meanwhile white is developing fast and you have no pieces developed.

user10570: The 3. .. Qe5+ is not a great continuation for black. Because:

It does not threaten anything really. White can block with developing (!) a bishop: 4. Be2.
It places blacks Queen in the center very early in the game where it will be a target of the attack for many whites pawns and pieces. Square e5 is far from a permanent position for the black queen, and black will spend several more queen moves, while white attacks the black queen with development. In short, the black queen certainly does not belong to e5.
Usual black continuations are 3. .. Qa5, 3. .. Qd6, and 3. .. Qd8. In all of them, the theme is to get the queen out of the potential harassment. I strongly suggest looking at 3. .. Qa5 and 3. .. Qd6 ideas as they entail quite different plans and lead to interesting games.


user13012: This is a bit trivial as an answer, but too long as a comment. You claim that you can develop "as good as White" but that is simply not true. White begins by interposing the Bishop 4.Be2. You play 4..Bg4. It is now a mistake to play 5.Nf3 because 5..Bxf3 spoils whites Pawns and makes his King insecure. But 5.d4! also gains a development tempo, and forces Black to choose one of the two moves that does not lose a piece.
If 5..Qe6, then I would choose 6.Bf4 from among many good moves. Then 6..c6 7.Qd3
and the contrast between positions is huge.
If 5. Bxe2, then Nxe2, with a similar outcome.
Perhaps you were only concerned about losing a tempo to Nf3 and forgot about d4? I think that White is close to winning. Even if not, you have a long and perilous defence to look forward to.

23844: <p>I'm new to chess (around 1000), and I like to practice the Scandinavian defence. I started to check the theory related to it, and I've never seen a single source talking about this queen move after Nc3.</p>

<pre><code>[FEN ""]
1.e4 d5 2.exd5 Qxd5 3.Nc3 Qe5+
</code></pre>

<p>I guess it's a bad one, otherwise they would mention it. But why is it a bad move? I've been playing this since I started (unconsciously) and I see no particular drawback (I just need to be careful not to make my queen stuck). </p>

<p>I understand that this opening violates the rule of development, but I don't feel the late when I play it. I often find a way to harasa my opponent (maybe it's because of my low rank, it becomes more visible at high rank?). Here are 2 variants I often end up with. As you can see I develop as good as white and I have even the queenside castling (almost) ready.</p>

<p>When defending with bishop:</p>

<pre><code>[FEN "eoui"]
1. e4 d5 2. exd5 Qxd5 3. Nc3 Qe5+ 4. Be2 Bg4
</code></pre>

<p>When defending with knight:</p>

<pre><code>[FEN ""]
1. e4 d5 2. exd5 Qxd5 3. Nc3 Qe5+ 4. Nge2 Bf5 5. d3 Nc6
</code></pre>
 14471: <p>Qe5+ is not a blunder or a mistake but it is definitely inaccurate play. Qa5 (most popular line) keeps a check on 2 central squares as well as Qd8.    </p>

<hr>

<blockquote>
  <p>Defending with bishop</p>
</blockquote>

<p>Also in the second line you mentioned (Bc2) after Bg4, white has an excellent move d5! Now white has a tempo in development, space as well as development whereas black is trying to play with two pieces. Once you play the recommended Bxe2 Nxe2 the advantage for white is apparent as black scrambles to position his queen and <em>start</em> development when white has two pieces and a pawn out in the game.<br>
This is why it's a bad idea to play Qe5+. It may not look like you're losing much but the advantage white has is more apparent the higher the level you play at.</p>
 4418: <blockquote>
  <p>But why it's a bad move?</p>
</blockquote>

<p>You are moving your queen to a square where it is going to be attacked again soon and then you will have to move the queen for a third time. Meanwhile white is developing fast and you have no pieces developed.</p>
 10570: <p>The 3. .. Qe5+ is not a great continuation for black. Because:</p>

<ol>
<li>It does not threaten anything really. White can block with developing (!) a bishop: 4. Be2.</li>
<li>It places blacks Queen in the center very early in the game where it will be a target of the attack for many whites pawns and pieces. Square e5 is far from a permanent position for the black queen, and black will spend several more queen moves, while white <strong>attacks the black queen with development</strong>. In short, the black queen certainly does not belong to e5.</li>
<li>Usual black continuations are 3. .. Qa5, 3. .. Qd6, and 3. .. Qd8. In all of them, the theme is to get the queen out of the potential harassment. I strongly suggest looking at 3. .. Qa5 and 3. .. Qd6 ideas as they entail quite different plans and lead to interesting games.</li>
</ol>
 13012: <p>This is a bit trivial as an answer, but too long as a comment. You claim that you can develop "as good as White" but that is simply not true. White begins by interposing the Bishop 4.Be2. You play 4..Bg4. It is now a mistake to play 5.Nf3 because 5..Bxf3 spoils whites Pawns and makes his King insecure. But 5.d4! also gains a development tempo, and forces Black to choose one of the two moves that does not lose a piece.</p>

<p>If 5..Qe6, then I would choose 6.Bf4 from among many good moves. Then 6..c6 7.Qd3
and the contrast between positions is huge.</p>

<p>If 5. Bxe2, then Nxe2, with a similar outcome.</p>

<p>Perhaps you were only concerned about losing a tempo to Nf3 and forgot about d4? I think that White is close to winning. Even if not, you have a long and perilous defence to look forward to.</p>
