Write electron configurations for a. the cations Sr^2+, Cs^+, In^+, and Pb^2+ . b. the anions P^

Write electron configurations for a. the cations Sr^2+,...

Key Concepts

Noble Gas Shorthand

The noble gas shorthand is a useful method for representing the electron configuration of an atom by abbreviating the core electrons with the symbol of the preceding noble gas. This simplification helps in focusing on the valence electrons which largely determine an element's chemical behavior, especially when writing configurations for cations and anions.

Electron Configuration

Electron configuration is the method used to describe the arrangement of electrons within an atom’s orbitals. It follows certain rules such as the Aufbau principle, which dictates that electrons fill the lowest energy orbitals first, along with Hund's rule and the Pauli exclusion principle that govern electron placement and occupancy. This concept is central to understanding chemical properties and reactivity.

Ion Formation (Cations and Anions)

The formation of ions involves the loss or gain of electrons relative to the neutral atom. Cations are formed when electrons are removed, typically from the highest energy (or outermost) orbitals, while anions are formed by the addition of electrons to the atom. Recognizing how electron removal or addition affects the overall electron configuration is crucial for correctly writing the configurations of ions.

Periodic Table Structure and Orbital Fillings

Understanding the structure of the periodic table is essential for writing electron configurations since it provides information about the order in which orbitals are filled. The placement of elements into s, p, d, and f blocks helps determine the sequence of orbital filling and the distribution of electrons. Additionally, changes due to ion formation must be considered in the context of the periodic table.

Transcript

00:01 So in this video we're going to talk about question 50 from chapter 8, which asks us to write the electron configurations for a, the cation, strontium plus 2, indium plus 1, indium plus 1, and lead plus 2, and the anions, phosphorus minus 3, sulfur minus 2, and bromine minus 1.

00:19 So let's start with strontium plus 2.

00:22 So where is strontium on the periodic table? so strontium is over here.

00:27 And when strontium has a plus 2 charge, meaning it's lost two electrons, it has the same electron configuration as krypton.

00:36 So how are we going to write it? well, we can abbreviate it a lot if we take the noble gas before that and use that to indicate the electron configuration up until that noble gas.

00:48 So the noble gas before it is argon.

00:51 So i'm going to write argon in brackets.

00:53 And then after argon, where do my electrons go? well, i have my 4s orbital, which can hold two electrons.

01:00 And my 3d orbital, which can hold 10 electrons, while my 4s orbital gets filled before my 3d orbital, when i write my electron configuration, i'm going to write the 3d orbital first.

01:12 And after my 3d orbital, i have my 4p orbital, which is gonna have six electrons in it, because we said we had the same electron configuration as krypton, so that's six electrons.

01:23 So i have my argon in brackets, then i have 3d10, 4s squared, and 4p6.

01:29 Next, we have cesium with a plus one charge.

01:32 So let's look where cesium is on the periodic tables.

01:35 That's one of our alkali metals that's over here.

01:37 So cesium with a plus one charge, if we take away electrons, if we take away one electron from cesium, then we have the same electron configuration as xenon.

01:46 So how are we going to write it? well, we can take the noble gas that comes before that, which is krypton, and write it in brackets.

01:53 So we have krypton in brackets.

01:55 Then what comes after krypton? after krypton comes our 5s orbital with two electrons in it and our 4d orbital with 10 electrons in it and then our 5p orbital with six electrons in it because we have the same electron configuration as xenon so six electrons so the electron configuration here is krypton 4d10 5s squared 5p to the six next we have indium with a plus one charge and so let's look for indium on the periodic table.

02:36 So indium is right here.

02:38 And indium with a plus one charge, we remove one electron.

02:41 We remove the only electron that's in our p orbital.

02:44 And so we're back down to our 5s orbital.

02:47 So how are we going to write this? well, we first write the noble gas that comes before that.

02:52 So that's krypton.

02:53 And then we have just two more electrons as that.

02:56 So we have 5s squared.

02:57 So for end on we have krypton 5s squared.

03:00 Next we have lead with a plus two charge.

03:03 So lead is here, pb...