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How do sub-atomic particles coexist in an electrically neutral atom?
Sub-atomic particles coexist in an electrically neutral atom with negatively charged electrons, positively charged protons, and electrically neutral neutrons.
Why is an atom of one element different from the atoms of other elements?
Atoms of different elements are different due to the number of protons in their nuclei which determines the element's identity and properties.
How many colours are there in a rainbow?
What are the characteristics of electromagnetic waves?
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What happens when you heat an iron rod on a flame?
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Why do different elements emit different flame colors when heated by the same non-luminous flame?
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What is the shape of an s-orbital?
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What is the shape of a p-orbital?
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What is the shape of a d-orbital?
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What is the maximum number of electrons that can occupy the d sub-shell?
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What is the spin quantum number denoted by?
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What term refers to the two possible orientations of the spin of an electron?
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Electrons with paired spins have parallel spins.
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How many electrons can occupy an orbital according to the Pauli Exclusion Principle?
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For a Carbon (C) atom with atomic number 6, where does the 6th electron go?
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In an atom, where do electrons begin to pair up based on Hund's Rule?
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The electromagnetic energy of light can have only certain discrete energy values given by the equation E=h$ u$. This is known as ________.
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In an atom, it is possible to accurately measure the position and velocity of an electron simultaneously.
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Match the following quantum principles with their descriptions:
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What does a line spectrum tell us about the structure of an atom?
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Why does an electron emit energy?
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Bohr's model successfully accounted for the splitting of line spectra into finer lines for hydrogen atoms.
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Why is the electron in an atom restricted to revolve around the nucleus at certain fixed distances? The electron is restricted in its movement due to ______.
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What kind of model replaced Bohr's atomic model to describe the behavior of electrons in an atom more accurately?
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Match the quantum numbers with their meanings:
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Study Notes
Structure of Atom
- Sub-atomic particles like negatively charged electrons, positively charged protons, and electrically neutral neutrons coexist in an electrically neutral atom.
Spectrum
- A rainbow is formed by the formation of seven colours, namely violet, indigo, blue, green, yellow, orange, and red (VIBGYOR).
- The colours of a rainbow spread continuously, and the intensity of each colour varies from one point to another.
- The wave nature of light is characterized by the production of ripples when a stone is thrown into a still pond.
- Electromagnetic waves are produced when an electric charge vibrates, and they have a speed of 3 × 10^8 m/s.
Electromagnetic Waves
- Electromagnetic waves have characteristics like wavelength (λ) and frequency (υ).
- The relation between wavelength and frequency is given by λα 1/υ or c = υλ.
- Electromagnetic waves can have a wide variety of frequencies, and the entire range of frequencies is known as the electromagnetic spectrum.
- The electromagnetic spectrum consists of a continuous range of wavelengths from gamma rays to radio waves.
- Visible light is a part of the electromagnetic spectrum, and it has a range of wavelengths from red to violet.
Atomic Model
- Niels Bohr proposed that electrons in an atom occupy 'stationary' orbits (states) of fixed energy at different distances from the nucleus.
- The energy of an electron in an atom can have only certain values, E1, E2, E3 ……, and the states corresponding to these energies are called stationary states.
- The lowest energy state of the electron is known as the ground state.
- When an electron gains energy, it moves to a higher energy level, the excited state.
- The electron loses the energy and comes back to its ground state, and the energy emitted is seen in the form of electromagnetic energy.
Bohr-Sommerfeld Model
- Bohr-Sommerfeld model added elliptical orbits to Bohr's atomic model to account for the structure (splitting) of line spectra.
- In this model, the nucleus of the atom is one of the principal foci of the elliptical orbits.
Quantum Mechanical Model
- The quantum mechanical model of an atom was developed by Erwin Schrodinger.
- According to this model, electrons do not follow definite paths in an atom.
- Instead of orbits, the electrons are thought to exist in a particular region of space around the nucleus at a given instant of time.
- The region of space around the nucleus where the probability of finding the electron is maximum is called an orbital.### Quantum Numbers and Atomic Orbitals
- Each orbital of a stable energy state for the electron is described by a set of three quantum numbers: n, l, and ml.
- These numbers indicate the probability of finding the electron in the space around the nucleus and describe the energy of the electrons.
Principal Quantum Number (n)
- n has positive integer values of 1, 2, 3, … and indicates the size and energy of the main shell.
- As n increases, the shells become larger, and the electrons are farther from the nucleus, with higher energy.
- Each n value has one main shell, represented by letters K, L, M, etc.
Angular Momentum Quantum Number (l)
- l has integer values from 0 to n-1 for each value of n.
- Each l value represents one sub-shell, with values designated by letters s, p, d, f, etc.
- The value of l for a particular sub-shell is related to the shape of the sub-shell in the space around the nucleus.
Magnetic Quantum Number (ml)
- ml has integer values between -l and l, including zero.
- The values of ml describe the orientation of the orbital in space relative to other orbitals in the atom.
- The number of ml values indicates the number of orbitals in a sub-shell with a particular l value.
Relationships Between Quantum Numbers
- The maximum number of electrons that can occupy a sub-shell is 2(2l+1).
- Each sub-shell holds a maximum of twice as many electrons as the number of orbitals in the sub-shell.
Shapes of Orbitals
- s-orbitals are spherical in shape.
- p-orbitals are dumbbell-shaped.
- d-orbitals are double dumbbell-shaped.
Spin Quantum Number (ms)
- ms has two possible values: +1/2 and -1/2, representing two possible orientations of the spin of an electron.
- The spin quantum number is important when electrons occupy specific orbitals in multi-electron atoms.
Electronic Configuration
- The distribution of electrons in shells, sub-shells, and orbitals in an atom is known as electronic configuration.
- The electronic configuration can be represented by the shorthand notation nl x, where n is the principal energy level, l is the letter representing the sub-level, and x is the number of electrons in the sub-shell.
- The electronic configuration of an atom is built up by placing electrons in the lowest available orbitals until the total number of electrons added is equal to the atomic number.
Pauli Exclusion Principle
- No two electrons of the same atom can have all four quantum numbers the same.
- If n, l, and ml are the same for two electrons, then ms must be different.
- An orbital can hold only two electrons, and they must have opposite spins.
Aufbau Principle
- Electrons are assigned to orbitals in order of increasing energy.
- The maximum number of electrons in a shell is 2n2, where n is the principal quantum number.
- The maximum number of electrons in a sub-shell is 2(2l+1), where l is the angular momentum quantum number.
Hund's Rule
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Electrons in degenerate orbitals have the same spin, and electron pairing starts only when all available empty orbitals of the same energy are singly occupied.### Atomic Orbitals
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The space around the nucleus where the probability of finding an electron is maximum is called an orbital.
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Three quantum numbers (n, l, ml) describe the energy, shape, and orientation of an atomic orbital.
Electron Configuration
- The arrangement of electrons in shells, sub-shells, and orbitals in an atom is called the electron configuration.
- According to Pauli's Exclusion Principle, no two electrons of the same atom can have all four quantum numbers the same.
- Aufbau principle: The lowest-energy orbitals are filled first.
- Hund's rule: The orbitals of equal energy (degenerate) are occupied with one electron each before pairing of electrons starts.
Electron Properties
- Spin is an intrinsic property of an electron.
- There are two possible spin orientations for an electron in an orbital: +½ and -½.
Quantum Numbers
- The quantum number n describes the energy of an orbital (or shell).
- The quantum number l describes the shape of an orbital (or sub-shell).
- The quantum number ml describes the orientation of an orbital (or sub-shell).
- The quantum number ms describes the spin of an electron.
Spectra
- Absorption spectrum: The spectrum of radiation absorbed by an atom.
- Emission spectrum: The spectrum of radiation emitted by an atom.
- Continuous spectrum: A spectrum of radiation with all wavelengths, such as a rainbow.
Bohr's Orbit
- An orbital is a three-dimensional region around the nucleus where the probability of finding an electron is maximum.
- Bohr's orbit is a two-dimensional circular path around the nucleus.
Shells and Sub-shells
- The maximum number of electrons that can be accommodated in a principal energy shell is 2n^2.
- The maximum number of electrons that can be accommodated in a sub-shell is 2(2l+1).
- The maximum number of electrons that can be accommodated in an orbital is 2.
- The number of sub-shells in a principal energy shell is (n-1).
- The spin orientations of an electron in an orbital are +½ and -½.
Specific Elements
- The electron configuration of nitrogen (Z=7) is 1s^2 2s^2 2p^3.
- The electron configuration of sodium (Na) is 1s^2 2s^2 2p^6 3s^1.
- There are exemptions in writing the electronic configurations of chromium and copper.
Light and Waves
- The wavelength of a radio wave is 1.0m, and its frequency can be calculated.
- The wavelengths and corresponding frequencies of three primary colors are:
- Red: 620-750 nm
- Blue: 450-495 nm
- Green: 520-560 nm
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Description
This quiz covers the basics of atomic structure, including sub-atomic particles like electrons, protons, and neutrons. Learn how these particles coexist in an electrically neutral atom.
