Chemistry Chapter on Periodic Table and Elements

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Questions and Answers

What characteristic defines diamagnetic materials?

Atoms with varying electron configurations

Atoms that are strongly attracted to magnetic fields

Atoms with unpaired electrons

Atoms with entirely paired electrons (correct)

Which scientist is known for formulating the Periodic Law?

Johann Döbereiner

John Dalton

Dmitri Mendeleev (correct)

Jons Berzelius

What did Mendeleev do to address undiscovered elements in his periodic table?

He predicted their properties and left gaps (correct)

He eliminated them from consideration

He marked them with a question mark

He included them in the table without properties

Which pioneer sought to establish a system of chemical symbols?

Jons Berzelius (C) Signup and view all the answers

What concept did John Newlands introduce related to the periodicity of elements?

Law of Octaves (A) Signup and view all the answers

How many elements were included in Dalton's first list?

5 elements (A) Signup and view all the answers

Which of the following was a major contribution of Johann Döbereiner?

Identifying chemically similar groups called triads (D) Signup and view all the answers

Which block of the periodic table includes elements with unfilled d orbitals?

d Block (A) Signup and view all the answers

What was the significant achievement of Don Eigler and colleagues in 1993?

Manipulation of individual atoms (C) Signup and view all the answers

What was the primary tool used by Don Eigler to create the electron-trapping barrier?

Low-temperature scanning tunneling microscope (D) Signup and view all the answers

What determines the total number of nodes present in the electron's wave function?

The energy level of the electron (D) Signup and view all the answers

If there are four nodes in the electron image, what is the energy level of the electron?

n = 5 (D) Signup and view all the answers

How many times deeper are the energy levels of He+ compared to those of hydrogen (H)?

Four times deeper (A) Signup and view all the answers

What complicates the calculation of states and energy levels in multielectron systems?

Electron-electron repulsion (C) Signup and view all the answers

What principle states that two electrons with the same spin cannot occupy the same orbital?

Pauli Exclusion Principle (D) Signup and view all the answers

What determines the properties of atoms and ions?

The arrangement of electrons (B) Signup and view all the answers

Which of the following statements is true regarding one-electron systems such as He+?

They are held closer to the nucleus due to increased nuclear charge. (D) Signup and view all the answers

Which relationship involves wavelength, frequency, and energy for light?

Energy = Planck's constant * Frequency (A) Signup and view all the answers

What is the phenomenon called when light ejects electrons from a metal surface?

Photoelectric effect (C) Signup and view all the answers

How does an electron transition from a higher to a lower energy level in a hydrogen atom?

By emitting a photon (C) Signup and view all the answers

What part of the electromagnetic spectrum does visible light occupy?

A middle range of wavelengths (A) Signup and view all the answers

What does the wave-particle duality of light imply?

Light exhibits properties of both waves and particles (A) Signup and view all the answers

What is the role of the threshold energy, or work function, in the photoelectric effect?

It is the minimum energy required to eject an electron (B) Signup and view all the answers

What influences the color of light?

The wavelength of the light (D) Signup and view all the answers

What effect do electron repulsions have on multielectron species?

They destabilize the electrons and increase potential energy. (D) Signup and view all the answers

How is effective nuclear charge (Zeff) calculated?

Zeff = Z - S (A) Signup and view all the answers

Which type of orbital experiences the highest effective nuclear charge?

s orbitals (A) Signup and view all the answers

What does Hund's Rule state about electron configuration in degenerate orbitals?

Electrons occupy degenerate orbitals singly first to avoid repulsions. (C) Signup and view all the answers

What determines the potential energy of electrons in a multielectron atom?

The effective nuclear charge experienced by the electrons. (A) Signup and view all the answers

Which of the following configurations corresponds to the element Phosphorus (P)?

1s2 2s2 2p3 (D) Signup and view all the answers

Which orbital type has the lowest penetration ability?

f orbitals (A) Signup and view all the answers

Which principle explains why electrons prefer to occupy degenerate orbitals singly before pairing?

Hund's Rule (D) Signup and view all the answers

What condition must be met for an electron to be ejected from a metal surface?

Ephoton > Ethreshold (C) Signup and view all the answers

Which of the following metals has the highest work function?

Lithium (A) Signup and view all the answers

How does the work function (Φ) change among different metals?

Φ decreases for alkali metals in order from lithium to cesium. (D) Signup and view all the answers

What is true about the relationship between the energy of the photon and the kinetic energy of the ejected electron?

The excess energy from Ephoton after overcoming Φ contributes to the kinetic energy. (B) Signup and view all the answers

What is the threshold frequency ($ u_t$) for calcium with a work function of $4.64 × 10^{-19}$ J?

$7.00 × 10^{14} Hz$ (C) Signup and view all the answers

Which of the following expressions correctly represents the relationship of energy for an electron and a photon?

$E_{photon} = Φ + E_{ejected}$ (D) Signup and view all the answers

What happens to the excess energy when Ephoton exceeds the work function Φ?

It contributes to the kinetic energy of the electron. (A) Signup and view all the answers

What is the energy required to eject one mole of electrons for calcium?

279 kJ mol^{-1} (B) Signup and view all the answers

What is the primary reason why electrons in a classical model of the atom would spiral into the nucleus?

The electrons lose energy due to continuous acceleration in a circular path. (D) Signup and view all the answers

What is the significance of the unique emission spectra of elements?

It provides evidence for the quantized nature of energy levels within atoms. (A) Signup and view all the answers

Which of the following statements accurately describes Bohr's model of the atom?

Electrons move in circular orbits around the nucleus with quantized energy levels. (B) Signup and view all the answers

What happens to an atom when it absorbs a photon of light?

The atom's electrons transition to a higher energy level. (B) Signup and view all the answers

Which of the following is a characteristic of an electron in an atom?

Electrons can only exist in specific, discrete energy levels. (A) Signup and view all the answers

What happens to an atom in an excited state?

The atom has gained energy and its electrons are at a higher energy level. (C) Signup and view all the answers

What is the relationship between energy levels and the frequency of emitted light?

The frequency of emitted light is directly proportional to the energy difference between energy levels. (B) Signup and view all the answers

What is the significance of the quantum mechanical model in explaining atomic behavior?

It explains why electrons in atoms can only occupy certain specific energy levels. (D) Signup and view all the answers

Study Notes

Unit 3 - Electrons in Atoms

Unit covers electrons in atoms, light, blackbody radiation, photoelectric effect, hydrogen atom, quantum mechanics, periodic table and electron configurations.

3.0 Unit Coverage

Topics include light, blackbody radiation, photoelectric effect, hydrogen atom, quantum mechanics, periodic table and electron configurations.

3.1 Introduction To Light

Light is an electromagnetic wave carrying energy.
Different colors (e.g., red, blue) correspond to different wavelengths (e.g., longer, shorter) and frequencies.
480 THz, 635 nm
510 THz, 590 nm
540 THz, 560 nm
610 THz, 490 nm
670 THz, 450 nm
750 THz, 400 nm

3.1 Electromagnetic Spectrum

Light is an electromagnetic wave carrying energy.
Different colors correspond to different wavelengths and frequencies.
The spectrum includes gamma rays, X-rays, ultraviolet, visible, infrared, microwaves, and radio waves.
The energy of light is inversely proportional to its wavelength.

3.1 Characterization Of Waves

Frequency (v): number of peaks passing a point per unit time (measured in Hz, where 1 Hz = 1 s⁻¹).
Wavelength (λ): distance between peaks (measured in meters). Nanometers (nm) are frequently used for visible light (1 nm = 10⁻⁹ m).

3.1 Speed Of Waves

The speed of light (c) is constant (approximately 2.9979 × 10⁸ m/s).
Wavelength (λ) is equal to the speed of light (c) divided by the frequency (v): λ = c/v

3.1 Electromagnetic Spectrum Revisited

Frequency and wavelength of light are inversely proportional.
The energy of light is proportional to frequency (E = hv), where h is Planck's constant.

3.2 Blackbody Radiation

All objects emit electromagnetic radiation due to thermal energy.
The radiation's intensity pattern depends on its temperature.

3.2 Ultraviolet Catastrophe

Classical wave theory failed to explain observed blackbody spectra at short wavelengths (ultraviolet catastrophe).

3.2 Max Planck and Quantization

Planck proposed that light energy is quantized, meaning it comes in discrete packets called photons.
The energy of a photon (Ephoton) is related to its frequency (ν) by Ephoton = hν, where h is Planck's constant (6.62606957×10⁻³⁴ Js).

3.3 Photoelectric Effect

Light striking a metal surface can eject electrons.
The emission of electrons depends on the frequency of light and not its intensity.
The maximum kinetic energy of emitted electrons depends linearly on the frequency of the incident light, once the threshold frequency (minimum frequency for emission) is exceeded.

3.3 Work Function

The threshold frequency (ν₀) is related the work function (Φ) by Φ=hν₀.
The relationship between the kinetic energy of the ejected electron (Ek), the incident light frequency (ν), and the work function (Φ) of the metal is Ek = hν − Φ.

3.3 Example - Threshold Frequency

The threshold frequency for calcium (given its work function) can be calculated using the equation ν= Φ/(h).

3.3 Example - Kinetic Energy

The kinetic energy of an ejected electron from calcium (for a given wavelength) is calculated using the formula Ekin = hv − Φ.

3.4 Emission Spectra of Elements

Each element produces a unique emission spectrum.

3.4 Discrete Energy Levels

Atoms have discrete energy levels, meaning electrons can only exist at specific energy levels.
Transitions between energy levels involve absorbing or releasing energy in the form of photons.

3.4 Hydrogen Atom

The hydrogen atom has a simple set of energy levels.
The energy level of hydrogen is given by the formula Eₙ = -Rᵢₑ/n² where n is an integer (1, 2, 3…); Rᵢₑ is equal to a constant that depends on the mass of the fundamental particles (electron, proton, etc.).

3.4 Energy of Electron Transition

Electron transitions between energy levels involve absorbing or emitting a photon with energy ΔE related to the energy levels via ΔE = ±hν.

3.4 Hydrogen Atom Examples

Calculate the frequency of emission lines when a hydrogen atom transitions.

3.5 Wave Functions

The solutions to Schrödinger's equation describe the state of an electron in an atom as a wave.
Ψ² gives the probability of finding an electron at a particular location.

3.5 Principal Quantum Number

The principal quantum number (n) describes the energy and distance of an electron from the nucleus.

3.5 Angular Momentum Number

The angular momentum quantum number (l) describes the shape of an electron's orbital.

3.5 Magnetic Quantum Number

The magnetic quantum number (ml) describes the orientation of an electron's orbital in space.

3.5 s Orbitals

s orbitals have a spherical shape.
The number of nodal spheres is n - 1, where n is the principal quantum number.

3.5 p Orbitals

p orbitals have a dumbbell shape.
A nodal plane separates the two lobes.
There are three degenerate p orbitals (mₗ = -1, 0, +1).

3.5 d Orbitals

d orbitals have a more complex cloverleaf shape.
There are five degenerate d orbitals (mₗ = -2, -1, 0, +1, +2).

3.5 Specifying Orbitals

The combination of the n, l, and mₗ designations specify an orbital.
This corresponds to an electron's motion around the nucleus.

3.5 Spin Quantum Number

Electrons exhibit spin, a property described by the spin quantum number with possible values of +½ or -½.
There are two states associated with the lowest energy level.

3.5 Hydrogen Energy Levels

The energy levels are related to the principal quantum number (n) by Eₙ = -Rᵢₑ/n², where Rᵢₑ is the Rydberg constant.
The number of orbitals associated with a given energy level is equal to n².

3.5 Orbitals and States of Hydrogen

Provides a table relating the values of n, l, the number of orbitals, and the total number of states, or electrons, for each energy level.

3.6 One Electron Systems

Ions with a single electron have the same orbitals as hydrogen, modified by the nuclear charge.

3.6 Multielectron Systems

Calculating energy levels is complicated by electron repulsions.
The Pauli Exclusion Principle dictates that no two electrons can have the same set of quantum numbers.
Electrons fill orbitals in order of increasing energy to minimize their mutual repulsion.

3.6 Ground State Electron Configurations

Aufbau's Principle: Electron configurations are determined by filling orbitals in order of increasing energy.

3.6 Electron Configuration Exceptions

In some elements, notably Cr and Cu, electron configuration exceptions occur because of the stabilization gained from particular half-filled and fully-filled subshells.

3.6 Diamagnetic vs Paramagnetic

A paramagnetic material has unpaired electrons, which align with external magnetic fields, making the material attracted to the field; diamagnetic materials do not have unpaired electrons and thus are repelled by the field.

3.6 Periodic Table Blocks

The s, p, d, and f blocks of the periodic table correspond to the filling of different types of electron orbitals.

3.6 Development of the Periodic Table

Describes the historical progression of organizing elements into a periodic table. Key contributors and their contributions are noted.

Additional Topics

3.5 Radial Probability Distributions: Visualizes the probability of finding an electron at various distances from the nucleus.
Spotlight in Engineering-Electron Corral: Describes an experiment demonstrating the wave-like nature of electrons.
Additional examples of electron configurations: Provides specific examples of writing electron configurations for various elements and ions.

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Description

Test your knowledge on the periodic table and the key concepts in chemistry related to elemental classification. This quiz covers historical figures, fundamental concepts, and the properties of materials in chemistry. See how well you understand the foundations of modern chemistry.