The Atom
3A: The Atomic Model
- Subatomic Particles: particles that are smaller than atoms
- Dalton suggested several properties of atoms:
- Elements are made of atoms
- Atoms are indivisible and cannot be destroyed
- The atoms of an element are all alike
- The atoms of one element are different from the atoms of all other elements, especially their masses
- Atoms combine chemically in small, whole number ratios
The Discovery of the Electron
- Law of Electrostatic Charges: the law that states that opposite electrical charges attract each other, while like charges repel each other
- Plum Pudding Model: the atomic model suggested negatively charged material with embedded electrons
- Thomson’s plum pudding model suggested negatively charged electrons embedded in a positive substance
The Nuclear Model
Alpha Particle: a helium nucleus that is emitted from a nucleus when a radioactive isotope experiences alpha decay
Nuclear Model: the atomic developed by Ernest Rutherford in which an atom is made up of a tiny, dense, positively charged central nucleus surrounded by negatively charged electrons
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Quantum Mechanics: the branch of physics that explores the behavior of matter and energy at the atomic and subatomic level
The Bohr Model
- Bohr Model: the atomic model developed by Niels Bohr in which electrons travel in distinct spherical regions called energy levels at fixed distances from the nucleus
- Energy Level: in the Bohr model of the atom; the regions located at fixed distances from the nucleus of an atom in which electrons are found
The Quantum-Mechanic Model
- Quantum - Mechanic Model: the currently accepted atomic model in which electrons are found in orbitals that are positioned around a nucleus that contains protons and (usually) neutrons
- the key factor that drove the development of the new atomic models is ^^workability^^
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3B: Atomic Structure
What is it like inside an atom?
- Electrons: the smallest of the main subatomic particles
- Proton: a subatomic particles located in the atom’s nucleus
- Neutron: carries no electrical charge
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Properties of Atoms
Atomic Number: the unique number of protons in the atoms of each element
Neutral Atom: an atom with balanced electric charges
- Neutron
- Relative mass: 1u
- Actual mass: 1.6749 x 10^-27 kg
- Symbol: n
- Charge: 0
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- Proton
- Relative mass: 1u
- Actual mass: 1.6726 x 10^-27 kg
- Symbol: p+
- Charge: +1e
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- Electron
- Relative mass: 1/1836u
- Actual mass: 9.1094 x 10^-31
- Symbol: e-
- Charge: -1e
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Mass Number
- Isotopes: atoms of the same element with differing numbers of neutrons
- Mass Number: the total number of particles found in the nucleus of a particular isotope of an element
- Isotope Notation: a symbol that distinguishes between different isotopes
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- Ions
- Ion: a charged atom or group of atoms that has gained or lost electrons, producing an unequal number of protons and electrons
- Anion: a negatively charged ion
- Cation: a positively charged ion
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- Atomic Mass: the weighted average of the masses of all naturally occurring isotopes of that element
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