What is an Atom

What Is an Atom?

Key Takeaways

• Atoms are the basic units of matter. Everything you see, touch, or breathe is made up of them.
• Atoms are unimaginably small. A few million stacked on top of each other would equal the thickness of a sheet of paper.
• Arrangement is everything. Whether a substance is hard like diamond or soft and slippery like graphite depends on how its atoms are linked and arranged..
• Atoms rule daily life. Processes like cooking, rusting, burning, and even colors and smells—all are outcomes of atomic interactions.

1) Concept: What Exactly Is an Atom?

The atom is the most basic particle of an element, yet it preserves the identity and nature of that element.

Think of it step by step:

• Atoms → Molecules → Substances
• Just as bricks → walls → house, or grains of sand → anthill, atoms come together to build the world around us.

???? In short: All matter is atomic in nature. Changing the way atoms are arranged or bonded results in different properties of the material.

2) How Small Are Atoms?

• Atoms are so small that they cannot be seen without the help of powerful instruments.
• Their size is usually measured in nanometres (nm).
• 1 nanometre (nm) = 10⁻⁹ metre.

For comparison: Stack a few million atoms in a line, and you’ll get roughly the thickness of a page from your notebook.

3) Relative Sizes (Scale of Comparison)

Here’s a quick idea of how big or small different things are:

Object (example)	Approx. Size (metres)
Hydrogen atom	~10⁻¹⁰ m
Water molecule	~10⁻⁹ m
Haemoglobin molecule	~10⁻⁸ m
Grain of sand	~10⁻⁴ m
Ant	~10⁻³ m
Apple	~10⁻¹ m

4) “Atoms Constantly Affect Everything Around Us”—What Does That Mean?

Atoms are not just tiny particles sitting idle.
The way atoms connect and organize gives each material its unique properties.

1. a) States of Matter (Solid, Liquid, Gas)

• Ice (solid): Atoms/molecules tightly packed → fixed shape.
• Water (liquid): Particles close but mobile → flows easily.
• Steam (gas): Particles far apart and moving rapidly → spreads to fill space.

Reason: Changing energy/temperature alters inter-particle forces and arrangements.

1. b) Chemical Reactions = Atoms Rearranging

• Everyday processes like cooking, rusting, and burning are actually just atoms reshuffling into new patterns.
• Example: Rusting of iron happens when iron atoms combine with oxygen and water molecules to form a new substance—iron oxide.

1. c) Physical Properties (Different Bonding Patterns)

• Diamond vs Graphite (both carbon):
• Diamond: Each carbon connects strongly in a 3D network → very hard.
• Graphite: Carbons form flat sheets that slide over one another → soft/slippery, used in pencils and lubricants.

1. d) Bonus Examples

• Conductor vs Insulator: Metals conduct electricity because their electrons move freely; plastics don’t because their electrons are tightly held.
• Colors and Smells: The exact way atoms are arranged in molecules decides how light is absorbed (color) and how your nose detects them (smell).

5) Can We “See” Atoms?

Normal microscopes can’t capture atoms. But advanced technologies like Scanning Tunnelling Microscope (STM) and Atomic Force Microscope (AFM) allow scientists to visualize and even manipulate individual atoms on surfaces.

6) Quick Glossary

• Atom: The basic building block of an element that retains its unique character.

• Molecule: Formed when two or more atoms join together, for example, the water molecule (H₂O).
• Bond: Attractive force holding atoms together.
• Nanometre (nm): 10⁻⁹ metre, a unit for atomic-scale measurement.

8) Summary (Quick Recap)

• Atoms form the foundation of all matter.
• They are tiny, measured in nm or Å.
• Material properties come from how atoms bond and arrange.
• Daily life activities (state changes, reactions, properties) are atomic in nature.
• With modern microscopes, scientists can map and study atoms.