Chemistry might seem daunting, but it's actually all around you...
Chemistry109 views·Updated Jun 11, 2026·4 pagesUnderstanding Chemistry: Atoms, Molecules, Compounds, and Mixtures
Corah@corahbretton
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The Basics of Matter
Everything you see is made of atoms - think of them as nature's building blocks. When atoms team up, they form molecules, and this is where chemistry gets interesting.
Compounds are formed when two or more different elements join forces chemically - like sodium and chlorine creating table salt. Mixtures, on the other hand, are just substances hanging out together without any chemical commitment, like oil and water.
Here's a golden rule that'll save you in exams: conservation of mass means the mass of what you start with always equals the mass of what you end up with. No atoms disappear - they just rearrange themselves.
Pro tip: When balancing equations, count atoms on both sides like you're checking your maths - they should always match up perfectly.
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Inside the Atom
Atoms are incredibly tiny - about 1 × 10⁻¹⁰ metres across, which means you could fit millions across the width of a human hair. The nucleus at the centre is 10,000 times smaller than the whole atom, yet contains nearly all its mass.
Every atom has an atomic number (number of protons) that determines what element it is. The mass number tells you the total protons plus neutrons. Think of protons as an element's ID card - hydrogen always has 1, helium always has 2.
Isotopes are like identical twins with different weights - same element, same number of protons, but different numbers of neutrons. Carbon-12 and carbon-13 are perfect examples, both carbon but with slightly different masses.
Remember: The number of protons never changes for an element - that's what makes carbon always carbon and oxygen always oxygen.
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Chemical Bonding
Compounds form when elements get together and actually bond chemically - it's like they're getting married rather than just dating. This happens through electrons being shared, given, or taken between atoms.
Ionic bonding occurs between metals and non-metals. The metal loses electrons (becoming positive), whilst the non-metal gains them (becoming negative). These opposite charges attract like magnets - think sodium chloride or magnesium oxide.
Covalent bonding happens when non-metals share electrons, creating molecules. Water, carbon monoxide, and nitrogen chloride are classic examples where atoms team up by sharing rather than transferring electrons.
Quick check: Metal + non-metal = ionic bonding, whilst non-metal + non-metal = covalent bonding.
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Separation Techniques and Atomic History
Scientists use different tricks to separate mixtures: crystallisation for getting solids from solutions, distillation for separating liquids with different boiling points, and chromatography for substances that dissolve differently.
The story of atomic discovery is brilliant. John Dalton imagined atoms as tiny, indivisible spheres. J.J. Thompson suggested the plum pudding model - a positive ball with electrons stuck in it like raisins.
Rutherford's alpha scattering experiment changed everything. By firing particles at gold foil, he discovered that atoms are mostly empty space with a tiny, dense nucleus. Niels Bohr then proposed that electrons orbit in specific energy levels or shells.
Fun fact: Most alpha particles went straight through the gold foil, proving atoms are mostly empty space - you're basically made of nothing!
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Chemistry109 views·Updated Jun 11, 2026·4 pagesUnderstanding Chemistry: Atoms, Molecules, Compounds, and Mixtures
Corah@corahbretton
Chemistry might seem daunting, but it's actually all around you - from the water you drink to the air you breathe. This chapter covers the fundamental building blocks of matter and how scientists figured out what atoms really look like...
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The Basics of Matter
Everything you see is made of atoms - think of them as nature's building blocks. When atoms team up, they form molecules, and this is where chemistry gets interesting.
Compounds are formed when two or more different elements join forces chemically - like sodium and chlorine creating table salt. Mixtures, on the other hand, are just substances hanging out together without any chemical commitment, like oil and water.
Here's a golden rule that'll save you in exams: conservation of mass means the mass of what you start with always equals the mass of what you end up with. No atoms disappear - they just rearrange themselves.
Pro tip: When balancing equations, count atoms on both sides like you're checking your maths - they should always match up perfectly.
2
of 4Sign up to see the content. It's free!
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Inside the Atom
Atoms are incredibly tiny - about 1 × 10⁻¹⁰ metres across, which means you could fit millions across the width of a human hair. The nucleus at the centre is 10,000 times smaller than the whole atom, yet contains nearly all its mass.
Every atom has an atomic number (number of protons) that determines what element it is. The mass number tells you the total protons plus neutrons. Think of protons as an element's ID card - hydrogen always has 1, helium always has 2.
Isotopes are like identical twins with different weights - same element, same number of protons, but different numbers of neutrons. Carbon-12 and carbon-13 are perfect examples, both carbon but with slightly different masses.
Remember: The number of protons never changes for an element - that's what makes carbon always carbon and oxygen always oxygen.
3
of 4Sign up to see the content. It's free!
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- Improve your grades
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Chemical Bonding
Compounds form when elements get together and actually bond chemically - it's like they're getting married rather than just dating. This happens through electrons being shared, given, or taken between atoms.
Ionic bonding occurs between metals and non-metals. The metal loses electrons (becoming positive), whilst the non-metal gains them (becoming negative). These opposite charges attract like magnets - think sodium chloride or magnesium oxide.
Covalent bonding happens when non-metals share electrons, creating molecules. Water, carbon monoxide, and nitrogen chloride are classic examples where atoms team up by sharing rather than transferring electrons.
Quick check: Metal + non-metal = ionic bonding, whilst non-metal + non-metal = covalent bonding.
4
of 4Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Separation Techniques and Atomic History
Scientists use different tricks to separate mixtures: crystallisation for getting solids from solutions, distillation for separating liquids with different boiling points, and chromatography for substances that dissolve differently.
The story of atomic discovery is brilliant. John Dalton imagined atoms as tiny, indivisible spheres. J.J. Thompson suggested the plum pudding model - a positive ball with electrons stuck in it like raisins.
Rutherford's alpha scattering experiment changed everything. By firing particles at gold foil, he discovered that atoms are mostly empty space with a tiny, dense nucleus. Niels Bohr then proposed that electrons orbit in specific energy levels or shells.
Fun fact: Most alpha particles went straight through the gold foil, proving atoms are mostly empty space - you're basically made of nothing!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Most popular content: Molecules and Compounds
2Most popular content in Chemistry
9Most popular content
9Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user