So, selenium 2 minus is what's going to be isoelectronic, because if you add two electrons to selenium, you'll get the same electron configuration that you have for krypton here.

负二价的硒离子将是等电子的，因为如果你给硒原子加上两个电子，你会得到,和氪原子相同的电子排布。

麻省理工公开课 - 化学原理课程节选

So, we need to fill our octet for selenium, so 1, 2, 3, 4.So, this is our Lewis structure here, hopefully you can see why it's not linear.

我们要填满硒原子的八配位，所以1，2，3，4。这就是Lewis结构，希望你们能看出来为什么它不是直线型的。

麻省理工公开课 - 化学原理课程节选