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The fundamental building blocks of matter include atoms and molecules.
- An atom is the smallest unit of matter that retains the characteristic properties of a chemical element.
- It is composed of even smaller particles called subatomic particles.
- These subatomic particles are neutrons, protons, and electrons.
- Molecules are made up of groups of atoms.
- They are the smallest units that define the chemical properties of a compound.
| Table of Content |
Key Terms: Atoms, Molecules, Electrostatic force, Covalent bond, Matter, Examples of atom, Examples of molecules, Chemical properties
What is an Atom?
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An atom is defined as the most fundamental unit of matter that forms a chemical element and retains all the properties of the element.
- They are composed of three types of subatomic particles: neutrons, protons, and electrons.
- Neutrons and protons are located at the nucleus of the atom, while electrons revolve around the nucleus.
- Examples: Li, C, N, O, etc.
Also check:
| Related Concepts | ||
|---|---|---|
| Atomic Orbitals | Atomic Radius | Energy level Diagram |
| Acids, Bases and Salts | Difference Between Element and Compound | Molecular Orbital Theory |
What is a Molecule?
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A molecule can be defined as a group of two or more similar or dissimilar atoms, bonded together by chemical bonds.
- It exhibits all the properties of the substance it composes.
- Breaking down a molecule reveals the properties of its constituent elements.
- Examples: H2O, HCl, NaCl, etc.
Difference Between an Atom and a Molecule
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Following are the differences between an atom and a molecule:
| Basis of Comparison | Atoms | Molecules |
|---|---|---|
| Definition | It is the smallest fundamental unit of an element which retains all the physical and chemical properties of that element. | It is formed by the chemical bonding of two or more atoms of the same or different elements and retains the physical and chemical properties of the element. |
| Structure | It is the smallest particle with the properties of an element. | It is a combination of two or more atoms. |
| Stability | Atomic stability can be affected by the arrangement of electrons in the outer shells. | Molecules are chemically stable, as the constituent atoms are bonded together through stable chemical bonds. |
| Constituents | An atom is made up of neutrons, protons, and electrons. | A molecule of an element or a compound is made up of two or more atoms. |
| Forces | Two types of force exist inside an atom i.e. electrostatic force and strong nuclear force. | The atoms in a molecule are held together either by strong electrostatic forces or by weak Van der Waal’s force. |
| Reactivity | Atoms of all elements except noble gases exhibit some degree of reactivity. | Molecules are generally less reactive than atoms because they share electrons, filling their outer shells. |
| Examples | Oxygen (O), Sulphur (S), Hydrogen (H), Phosphorus (P), etc. | Oxygen (O2), Sulphur (S8), Water (H2O), Phosphorus (P4), etc. |
Also check:
| Related Concepts | ||
|---|---|---|
| Precipitation reaction | Importance of pH in everyday life | Soaps and Detergents |
| Non-Metals | Metals and Non-Metals Formula and Equation | Components of Ecosystem |
Things to Remember
- An atom is the smallest unit of matter that forms a chemical element and retains all the properties of the element.
- An atom consists of electrons, protons, and neutrons.
- A molecule is a group of two or more similar or dissimilar atoms, bonded together by chemical bonds.
- Valence electrons make atoms unstable, forcing them to combine and form molecules.
- Molecules are chemically stable.
Sample Questions
Ques. What does atom mean? (2 Marks)
Ans. An atom is defined as the smallest or the most fundamental unit of matter that forms a chemical element and retains all the properties of the element and atoms are chemically unstable.
Ques. What is a molecule? (2 Marks)
Ans. A molecule can be defined as a group of two or more similar or dissimilar atoms, bonded together by chemical bonds, which can exist in a free state and retain the composition as well as the chemical characteristics of the element or compound.
Ques. Can atoms be created? (1 Mark)
Ans. As per the law of conservation of mass, no matter can neither be created nor destroyed. Atoms being the most building unit of all matter, can neither be created nor be destroyed.
Ques. What type of forces exist in an atom? (2 Marks)
Ans. Two types of force exist inside an atom. Electrostatic force of attraction holds the revolving electrons inside an atom pulling it closer to the nucleus. Strong nuclear force binds the neutrons and protons inside the nucleus of an atom.
Ques. What type of forces exist in a molecule? (2 Marks)
Ans. The atoms in a molecule are held together either by strong electrostatic forces between oppositely charged ions in the case of electrostatic bonds or weak Van der Waal’s force in the case of covalent bonds.
Ques. Is an atom considered as a molecule? (3 Marks)
Ans. In the kinetic theory of gases, the term "molecule" can refer to any gaseous particle, regardless of its structure. However, in chemistry, molecules are typically formed by atoms covalently bonded together. Complexes held by non-covalent interactions (like hydrogen bonds or ionic bonds) are not usually considered independent molecules. Elements themselves are not molecules; rather, molecules are the building blocks of matter.
Ques. How do atoms become molecules? (2 Marks)
Ans. Atoms form molecules by sharing or exchanging electrons, creating chemical bonds that hold them together. Only the outermost electrons, called valence electrons, participate in these bonds.
Ques. Is Salt a molecule? (2 Marks)
Ans. No, table salt (NaCl) is not a molecule. Molecules are held together by covalent bonds, where electrons are shared between atoms. In contrast, table salt is an ionic compound. It's formed by the attraction between oppositely charged ions (sodium cations and chloride anions) held by ionic bonds.
Ques. What are the examples of atoms? (1 Mark)
Ans. Oxygen (O), Sulphur (S), Hydrogen (H), Phosphorus (P), etc. are examples of an atom.
Ques. What are the examples of a molecule? (1 Mark)
Ans. Oxygen (O2), Sulphur (S8), Water (H2O), Phosphorus (P4), etc. are the examples of a molecule.
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