# Blocks of the periodic table

> s, p, d and f: what puts an element in each region


## Objectives

- Explain that an element's block (s, p, d or f) is the type of sublevel that receives its last electron.
- Locate the s- and p-blocks: the representative elements (groups IA to VIIA) and the noble gases (group 0).

## 1. The transition elements and their series




## 2. Four coloured regions

Predict: what decides an element's region?

- Whether it is a metal or a nonmetal
- The type of sublevel that receives its last electron ✓
- Its atomic mass

An element's block is set by the type of sublevel that receives its last electron: s, p, d or f.

[ar-EG] الـ block بتاع العنصر بيتحدد بنوع الـ sublevel اللي بياخد آخر electron: s أو p أو d أو f.
## 3. Blocks follow the last electron

block A region of the table whose elements get their last electron in the same type of sublevel. Sodium ends with $3s^1$, so it is in the s-block. Chlorine ends with $3p^5$, so it is in the p-block. The s-block (left) and the p-block (right) The width fits the sublevel. s holds 2 electrons, so the s-block has 2 columns. p holds 6, so 6 columns.


## 4. Groups of the s- and p-blocks

The s- and p-blocks sit on both sides of the long form of the table. They hold the **representative elements** (groups IA to VIIA) and the **noble gases** (group 0). Groups of the s- and p-blocks (n = the period number) Notice: for groups IA to VIIA, the Roman numeral counts the electrons in the outer level. The middle columns get different labels, which you'll meet in Chapter 1.


## 5. Find the block

Aluminum, $\ce{_{13}Al}$, is $[\text{Ne}]\ 3s^2\ 3p^1$. Which block and group is it in?

- p-block, group IA (1)
- p-block, group IIIA (13) ✓
- d-block, group IIIB (3)
- s-block, group IIA (2)

The last electron of aluminum enters 3p, so it is in the p-block. Its outer level holds 2 + 1 = 3 electrons, so it is in group IIIA (13).

[ar-EG] آخر electron في الـ aluminum بيدخل الـ 3p، فهو في الـ p-block. والمستوى الخارجي فيه 2 + 1 = 3 electrons، فهو في group IIIA (13).
## 6. Summary

Block = the type of sublevel that receives the last electron. The s- and p-blocks hold the representative elements (IA to VIIA) and the noble gases (group 0). The d-block is in the middle; the f-block is the two rows at the bottom. Elements of the **(s) and (p) blocks** are found **on both sides of the long form of the periodic table**. Chapter 1 starts with the elements between the s- and p-blocks. Can you explain why Na and Cl are in different blocks, though both are in period 3? Sodium ends with $3s^1$: its last electron enters an s sublevel, so it is in the s-block. Chlorine ends with $3p^5$: its last electron enters a p sublevel, so it is in the p-block. The block follows the type of sublevel, not the period.



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