## 1E-11

305303255
Posts: 40
Joined: Thu Jul 25, 2019 12:16 am

### 1E-11

Can somebody help me out and give a quick summary of how you find an electron configuration by doing it for one of the atoms in 1E-11?

Write the ground-state electron configuration for each of the following atoms: (a) sodium; (b) silicon; (c) chlorine; (d) rubidium.

Kevin Antony 2B
Posts: 99
Joined: Sat Sep 07, 2019 12:16 am

### Re: 1E-11

For sodium, it would look like this: [Ne] 3s^1

If you look at a periodic table, the closest element before Na with a full octet is Neon, so we start with [Ne]. From there, the valence electrons of Na fill up to the 3s^1 so we write that after.

Jiyoon_Hwang_2I
Posts: 101
Joined: Sat Sep 14, 2019 12:17 am

### Re: 1E-11

The ground-state electron configuration for sodium would be 1s^2 2s^2 2p^6 3s^1. However, you can also use a shortcut by determining the closest noble gas to the given element (in this case neon is the closest noble gas to sodium) and then writing the electron configuration starting at this noble gas. So, for sodium the short cut electron configuration would be [Ne] 3s^1

Justin Vayakone 1C
Posts: 110
Joined: Sat Sep 07, 2019 12:19 am

### Re: 1E-11

Electron configuration is just an easy way to see where all of the electrons are in the orbitals. When we are stating all of the orbitals, we start from lowest energy to highest energy. The periodic table is a great way to figure out what orbitals are occupied. Here is a link to see the periodic table organized by orbitals : https://www.ptable.com/#Orbital . Just go from left to right through the periodic table when writing the orbitals. For example, electron configuration of Na is: 1s^2 2s^2 2p^6 3s^1. Each orbital is written with a number superscript that describes how many electrons are in that orbital (3s^1 means only one electron is in 3s orbital). There is a way to shorten the electron configuration too. By using noble gases to replace all of the orbitals, we can shorten the configuration, so the electron configuration of Na could also be stated as [Ne] 3s^1.
Last edited by Justin Vayakone 1C on Sun Oct 20, 2019 8:27 pm, edited 1 time in total.

Kyla Grunden 1L
Posts: 46
Joined: Sat Sep 07, 2019 12:16 am

### Re: 1E-11

There are several ways to do this, but I think the best way if you're just learning this is to think about how many electrons can fit in each shell and subshell. To do this, here's a quick cheat sheet that will help you figure out the order electrons fill. You end up accidentally memorizing it pretty quickly!

a)Sodium has 11 electrons: it first fills 1s (2 electrons) then 2s (2 electrons), then 2p (6 electrons, we're now at 10 electrons total), and the remaining electron fills the 3s shell.

The configuration is 1s2 2s2 2p6 3s1

b) Silicon has 14 electrons: it first fills 1s (2 electrons) then 2s (2 electrons), then 2p (6 electrons) , then 3s (2 electrons, we're now at 12 electrons total), and the remaining 2 electrons fill the 3d shell.

1s2 2s2 2p6 3s2 3p2

c) Chlorine has 17 electrons: it first fills 1s (2 electrons) then 2s (2 electrons), then 2p (6 electrons) , then 3s (2 electrons, we're now at 12 electrons total), and the remaining 5 electrons fill the 3d shell.

The configuration is 1s2 2s2 2p6 3s2 3p5

d) Rubidium has 37 electrons, I'm going to do noble gas configuration to save time. This is where you use the configuration of the noble gas BEFORE the element you want the configuration of as a sort of stand in for the beginning of a configuration.

The noble gas before rubidium is Krypton (36 electrons). The remaining electron fills the 5s shell.

The noble gas configuration is [Kr] 5s1

Hope this helps!