We can write out what it is for any certain atom or ion x, X so it's just x plus an electron gives us x minus.

我们可以用，X，来表示一个任意的原子或离子，因此可以写成，X，加一个电子等于负一价的。

youdao

Namely, we will be saying the /a normal vector is x, y, z over a, plus or minus depending on whether we want it pointing in or out.

我们容易知道,法向量为，正负号取决于它是指向外面还是里面。

youdao

Therefore the acceleration since I call - that the "plus x direction"-- that was my plus sign-- must come out plus.

因此加速度必然,是在x正方向-,这里是正好，必然如此。

youdao