# Electric charges: attraction and repulsion

> The pull and the push inside every atom


## Objectives

- State that like charges repel and unlike charges attract.
- Predict how the force changes with the amount of charge and with distance.
- Apply the two rules to the nucleus and the electrons of an atom.

## 1. Electric charges: attraction and repulsion: from zero




## 2. A pull and a push

Two electrons are close to each other. What happens?

- They repel each other ✓
- Nothing happens, because electrons are too small
- They attract each other

Both electrons carry a negative charge, and like charges repel, so the two electrons push each other apart.

[ar-EG] الـ electrons الاتنين شايلين negative charge، والـ like charges بتتنافر، فالاتنين بيزقّوا بعض بعيد.
## 3. Like charges repel, unlike charges attract

Electric charges There are two kinds of charge, positive (+) and negative (−). Like charges repel; unlike charges attract. + and − attract. − and − repel. + and + repel. In an atom, the protons in the nucleus are positive and the electrons are negative. So the nucleus attracts the electrons. Electrons in an atom feel the pull of the nucleus and nothing else.


## 4. Stronger or weaker?

Change the charge of the nucleus and the distance to the electron. Watch the pull. Charge of the nucleus (number of protons) Distance from the nucleus Pull on the electron (to compare only) Tried both sliders? Tap to see the pattern More charge → stronger attraction. Smaller distance → stronger attraction. The same two rules hold for the repulsion between two electrons.


## 5. Attract or repel?

Atom X has 11 protons and atom Y has 17 protons. Their outer electrons are at about the same distance from the nucleus. Which nucleus pulls its outer electrons more strongly?

- Y, because its nucleus has more positive charge ✓
- Both pull equally, because the distance is the same
- X, because it has fewer protons

With the distance fixed, more protons means a stronger nuclear attraction.

[ar-EG] طالما المسافة ثابتة، protons أكتر يعني nuclear attraction أقوى.
## 6. Summary

Like charges repel; unlike charges attract. More charge or less distance means a stronger force. In an atom, the nucleus attracts the electrons; the electrons repel each other. Words the book uses **nuclear attraction** to electrons; **repulsion force** between electrons (Ch.1 p.12-13). Back to the hook (coming up in Ch.1) From Cr to Cu, more nuclear charge pulls; the extra 3d electrons push. Ch.1 explains this tug-of-war. Can you explain why adding more electrons to the same atom makes them push each other apart? All electrons carry a negative charge, and like charges repel. So the electrons in an atom push each other apart, and more charge means a stronger force.



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