# Ionization potential (ionization energy)

> How much energy does it take to pull an electron off?


## Objectives

- Define ionization potential (also called ionization energy) and its unit, kJ/mol.
- Explain why successive ionization energies increase, and why a big jump appears when an electron must leave a stable inner level.
- Use successive ionization energies to find the oxidation state of a representative metal.

## 1. Electronic configurations and oxidation states




## 2. Why is sodium only +1?

Predict: why does sodium stop at +1?

- Sodium has only one electron to give
- The second electron is farther from the nucleus
- Removing a second electron costs far more energy ✓

Sodium's 1st electron comes from 3s, but the 2nd must leave the stable [Ne] arrangement in level n = 2, nearer the nucleus, so it costs far more energy (4562 vs 496 kJ/mol). That big jump is why sodium stops at +1.

[ar-EG] أول electron في الـ sodium بيطلع من الـ 3s، لكن التاني لازم يسيب ترتيب الـ [Ne] المستقر في المستوى n = 2، اللي أقرب للـ nucleus، فبيحتاج طاقة أكبر بكتير (4562 مقابل 496 kJ/mol). الـ big jump ده هو السبب إن الـ sodium بيقف عند +1.
## 3. Ionization potential

Ionization potential (ionization energy) The energy needed to remove the most loosely held electron from a gaseous atom. Also called ionization energy. Sodium: 496 kJ/mol The unit is kJ/mol. The farther the electron is from the nucleus, the weaker the pull, so less energy is needed.


## 4. Strip a sodium atom

Remove sodium's electrons one after another. Watch what each one costs. electron removed energy for electron 1 1st electron: from 3s (n = 3). $\ce{Na -> Na+}$, now [Ne] energy for electron 2 2nd electron: from 2p (n = 2). $\ce{Na+ -> Na^{2+}}$ energy for electron 3 3rd electron: from 2p (n = 2). $\ce{Na^{2+} -> Na^{3+}}$ Successive ionization energies The energies needed to remove the 1st, 2nd, 3rd … electrons of an atom, one after another.


## 5. The big jump

Successive ionization energies of sodium Each one is larger: the electron leaves an ion that is more and more positive. The 2nd costs about 9 times the 1st. It must leave the stable [Ne] arrangement, in level n = 2, nearer the nucleus. So sodium gives up one electron only. The big jump tells you a representative metal's oxidation state.


## 6. Read the data

Metal X has these successive ionization energies: 578, 1817, 2745, 11577 kJ/mol. Which oxidation state does X show in its compounds?

- +4
- +3 ✓
- +1
- +2

578 → 1817 → 2745 rise steadily; 11577 is the big jump. So X shows +3.

[ar-EG] 578 → 1817 → 2745 بيزيدوا بالتدريج؛ والـ 11577 هي القفزة الكبيرة. يبقى الـ X بيظهر بـ +3.
## 7. Summary

Ionization potential (ionization energy): the energy to remove the most loosely held electron from a gaseous atom, in kJ/mol. Successive ionization energies increase, because each electron leaves a more positive ion. A big jump appears when the electron must leave a stable inner level: Na stops at +1. The big jump shows how many electrons a representative metal gives up. Next in Chapter 1: vanadium's energies rise gradually, with no big jump after its 4s electrons. Can you explain why sodium forms $\ce{Na+}$ but never $\ce{Na^{2+}}$?



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