Atoms
* The building blocks: Atoms are the fundamental units of matter. They consist of a nucleus (containing protons and neutrons) surrounded by a cloud of electrons.
* Basic units: They are the smallest unit of an element that retains the chemical properties of that element.
* Examples: Hydrogen (H), Oxygen (O), Carbon (C)
Molecules
* Two or more atoms bonded together: Molecules are formed when two or more atoms bond chemically to each other.
* Stable units: They are generally stable and have their own unique properties.
* Examples: Water (H₂O), Carbon Dioxide (CO₂), Glucose (C₆H₁₂O₆)
Ions
* Charged atoms or molecules: Ions are formed when an atom or molecule gains or loses one or more electrons, resulting in a net electrical charge.
* Cations and Anions: If an atom loses electrons, it becomes positively charged and is called a cation. If an atom gains electrons, it becomes negatively charged and is called an anion.
* Examples: Sodium ion (Na⁺), Chloride ion (Cl⁻), Sulfate ion (SO₄²⁻)
Key Differences in a Table:
| Feature | Atoms | Molecules | Ions |
|---|---|---|---|
| Definition | Fundamental units of matter | Two or more atoms bonded together | Charged atoms or molecules |
| Charge | Neutral | Neutral | Positive or negative |
| Examples | Hydrogen (H), Oxygen (O) | Water (H₂O), Carbon Dioxide (CO₂) | Sodium ion (Na⁺), Chloride ion (Cl⁻) |
| Stability | Can exist independently | Generally stable | Generally stable |
| Bonding | Not applicable | Covalent or ionic bonds | Not applicable (except in ionic compounds) |
Important Note:
* Ionic compounds are formed when cations and anions attract each other due to their opposite charges. These compounds are not technically "molecules" because they don't involve the sharing of electrons (covalent bonding).
* Polyatomic ions are ions that contain more than one atom. For example, the sulfate ion (SO₄²⁻) consists of one sulfur atom and four oxygen atoms.
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