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21 Dec 2025

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2 pages

Understanding Atomic Structure and Isotopes for OCR A Level Chemistry

anna🦋🧬📓🔬

@biannnl

Ever wondered what makes up everything around you? Atoms are... Show more

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## 2.1.1 Atomic Structure and isotopes
- Atoms the smallest parts of an element that can

Atomic Structure and the Basics

Think of an atom as the smallest piece of an element that can still take part in chemical reactions. Here's the surprising bit - atoms are mostly empty space! It's a bit like a football stadium with just a marble at the centre.

All the mass of an atom is packed into the tiny nucleus at its centre. This nucleus contains two types of particles: protons (positively charged) and neutrons (no charge). Both have a relative mass of 1, making them the heavyweight champions of the atomic world.

Electrons zoom around this nucleus like planets orbiting the sun, but they're incredibly light - about 2000 times lighter than protons or neutrons. These negatively charged particles create a 'cloud' around the nucleus. The electrostatic attraction between the positive nucleus and negative electrons is what keeps the whole atom together.

Key Point: Atoms are neutral overall because they have equal numbers of protons and electrons, so the positive and negative charges cancel out perfectly.

Ions and Isotopes - When Atoms Change

When atoms gain or lose electrons, they become ions - charged particles that behave very differently. Cations are positively charged because they've lost electrons (fewer electrons than protons). Anions are negatively charged because they've gained extra electrons.

Isotopes are like identical twins with different weights - they're atoms of the same element with identical numbers of protons and electrons, but different numbers of neutrons. This means they have the same atomic number but different mass numbers.

Here's what's brilliant about isotopes: they have identical chemical properties because they have the same number of electrons in their outer shells. Since electrons control chemical reactions, isotopes react in exactly the same way. However, their physical properties differ slightly because extra neutrons add mass without changing the chemistry.

Remember: Neutrons are like adding extra weight to a car - it makes it heavier and affects things like density, but it doesn't change how the engine works!

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21 Dec 2025

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2 pages

Understanding Atomic Structure and Isotopes for OCR A Level Chemistry

anna🦋🧬📓🔬

@biannnl

Ever wondered what makes up everything around you? Atoms are the tiny building blocks of all matter, and understanding their structure is crucial for mastering chemistry. Let's break down how these incredibly small particles work and why they behave the... Show more

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Atomic Structure and the Basics

Key Point: Atoms are neutral overall because they have equal numbers of protons and electrons, so the positive and negative charges cancel out perfectly.

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Ions and Isotopes - When Atoms Change

Remember: Neutrons are like adding extra weight to a car - it makes it heavier and affects things like density, but it doesn't change how the engine works!