# Energy sublevels (s, p, d, f)

> Why the d block has ten columns


## Objectives

- State that main energy level n has n sublevels.
- Give the maximum number of electrons in s, p, d and f: 2, 6, 10 and 14.
- Explain why the d sublevel first appears at n = 3.

## 1. Energy sublevels (s, p, d, f): from zero




## 2. Ten columns in the middle

Predict: why 10 columns?

- Because the sublevel filled there holds up to 10 electrons ✓
- Because each period has 10 elements
- Because only 10 such elements are known

In the middle block, the d sublevel is being filled, and a d sublevel holds up to 10 electrons: one column for each electron.

[ar-EG] في البلوك اللي في النص، الـ d sublevel هو اللي بيتملي، والـ d sublevel بيشيل لحد 10 electrons: عمود لكل electron.
## 3. Levels are divided into sublevels

Energy sublevels The parts that a main energy level is divided into: s, p, d and f. Number of sublevels = n. Each sublevel holds at most: s 2, p 6, d 10, f 14. Every main energy level has all four sublevels: s, p, d and f.


## 4. Open a level

Choose a main level. See which sublevels it has. Main energy level (n) K (n = 1): **1s** → 2 electrons L (n = 2): **2s, 2p** → 2 + 6 = 8 electrons M (n = 3): **3s, 3p, 3d** → 2 + 6 + 10 = 18 electrons N (n = 4): **4s, 4p, 4d, 4f** → 2 + 6 + 10 + 14 = 32 electrons Sublevels Maximum electrons (2n²) Add up the sublevels: you get the $2n^2$ of the level.


## 5. Which sublevels exist?

Which sublevel does NOT exist?

- 2p
- 3d
- 4f
- 2d ✓

2d does not exist: level 2 has two sublevels, 2s and 2p, and the d sublevel first appears at n = 3. 2p, 3d and 4f exist.

[ar-EG] الـ 2d مش موجود: المستوى 2 فيه 2 sublevels، 2s و 2p، والـ d sublevel أول ظهور ليه عند n = 3. أما الـ 2p والـ 3d والـ 4f فموجودين.
## 6. Summary

Main level n has n sublevels: 1s; 2s 2p; 3s 3p 3d; 4s 4p 4d 4f. Maximum electrons: s 2, p 6, d 10, f 14. The d sublevel first appears at n = 3 (3d). Back to the hook: exam wording The d sublevel can take up to **ten electrons**, so the d block contains **ten vertical columns** (Ch.1 p.3). Can you explain why there is a 3d sublevel but no 2d? Level n has n sublevels. Level 2 has only 2s and 2p, so there is no 2d. The d sublevel first appears at n = 3 (3d).



Chapter: Transition Elements (https://yaani.ai/ar/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/ar/lesson/chem-s3-en.lesson-atom.sublevels