Atom: Difference between revisions
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Electrons move around the nucleus in defined energy levels known as shells or orbitals. These energy levels are crucial for chemical bonding and reactions. | Electrons move around the nucleus in defined energy levels known as shells or orbitals. These energy levels are crucial for chemical bonding and reactions. | ||
= Atomic Number and Mass Number= | ==Atomic Number and Mass Number== | ||
* Atomic Number (Z): The number of protons in an atom, which determines the element. | * Atomic Number (Z): The number of protons in an atom, which determines the element. | ||
* Mass Number (A): The sum of protons and neutrons in the nucleus. | * Mass Number (A): The sum of protons and neutrons in the nucleus. | ||
* Isotopes: Atoms of the same element with different numbers of neutrons, leading to variations in atomic mass. | * Isotopes: Atoms of the same element with different numbers of neutrons, leading to variations in atomic mass. | ||
= Properties of Atoms= | |||
==Properties of Atoms== | |||
Atoms exhibit several fundamental properties: | Atoms exhibit several fundamental properties: | ||
* Size: Typically in the range of picometers (1 pm = 10⁻¹² m). | * Size: Typically in the range of picometers (1 pm = 10⁻¹² m). | ||
* Charge: Atoms are electrically neutral unless they lose or gain electrons to form ions. | * Charge: Atoms are electrically neutral unless they lose or gain electrons to form ions. | ||
* Reactivity: Dependent on the arrangement of electrons in the outermost shell. | * Reactivity: Dependent on the arrangement of electrons in the outermost shell. | ||
= Atomic Theories= | |||
==Atomic Theories== | |||
Several theories have been proposed to explain atomic structure: | Several theories have been proposed to explain atomic structure: | ||
* Dalton's Atomic Theory (1803): Proposed that atoms are indivisible and combine to form compounds. | * Dalton's Atomic Theory (1803): Proposed that atoms are indivisible and combine to form compounds. | ||
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* Bohr’s Model (1913): Introduced quantized electron orbits. | * Bohr’s Model (1913): Introduced quantized electron orbits. | ||
* Quantum Mechanical Model: The modern atomic theory describing electron probability clouds instead of fixed orbits. | * Quantum Mechanical Model: The modern atomic theory describing electron probability clouds instead of fixed orbits. | ||
= Importance of Atoms in Chemistry= | |||
==Importance of Atoms in Chemistry== | |||
Atoms play a crucial role in: | Atoms play a crucial role in: | ||
* Chemical Reactions: Atoms rearrange to form new substances through bonding. | * Chemical Reactions: Atoms rearrange to form new substances through bonding. | ||