Structure and Properties of Matter

Question 1

Dalton discovered 3 things, and they are?

Answer 1

The Law of Conservation of Mass
The Concept of Elements
The Law of Definite Composition (or Definite Proportions)

Question 2

What was Thompson’s wrong model of the atom?

Answer 2

The Thomson model of the atom, also known as the “plum pudding model,” was proposed by British physicist J.J. Thomson in 1904. It was one of the earliest attempts to describe the structure of the atom.

In this model, the atom is envisioned as a spherical cloud of positive charge with negatively charged electrons (the “plums”) embedded within it, similar to raisins or plums scattered within a pudding or dough.

The plum pudding model was eventually replaced after Ernest Rutherford’s gold foil experiment in 1911, which showed that atoms have a tiny, dense nucleus at their center, surrounded by mostly empty space. This discovery led to the development of the nuclear model of the atom, where the electrons orbit a central nucleus, rather than being embedded in a diffuse positive “pudding.”

While the Thomson model was later shown to be incorrect, it was an important step in the development of atomic theory.

Question 3

What was Rutherford’s correct model of the atom?

Answer 3

Ernest Rutherford’s model of the atom, developed after his famous gold foil experiment in 1909, is often called the “nuclear model” of the atom. This was a major advancement over J.J. Thomson’s “plum pudding” model and laid the groundwork for later atomic models, including the Bohr model.

Although Rutherford’s model was a breakthrough in understanding atomic structure, it wasn’t the final model. It was later refined by Niels Bohr in 1913, who incorporated ideas from quantum theory to explain the stability of electrons in orbit and the emission of specific wavelengths of light.

Key Features of Rutherford’s Nuclear Model:
The Atom is Mostly Empty Space
There is a Nucleus
The Electrons Orbit the Nucleus
The Nucleus Contains Most of the Atom’s Mass

Question 4

What was the ultraviolet catastrophe?

Answer 4

In summary, the ultraviolet catastrophe was a paradox in classical physics that predicted infinite energy emission at high frequencies, but this was resolved by Planck’s introduction of quantization in 1900, which was a cornerstone of the development of quantum mechanics.

As the frequency of radiation increases (particularly into the ultraviolet and beyond), the Rayleigh-Jeans law predicts that the energy emitted would keep increasing without limit. This was called the “ultraviolet catastrophe” because it suggested an absurd scenario: objects would emit an infinite amount of energy at ultraviolet and higher wavelengths, which was clearly unphysical and did not match experimental data.

Question 5

What were James Maxwell’s theories about electromagnetic radiation?

Answer 5

1. The distribution of electric charges creates an electric field, and a MOVING electric field generates a magnetic field.
2. Electromagnetic radiation exists in WAVES that are created by oscillating (i.e. vibrating) particles (i.e. atoms and molecules).

Question 6

What is a photon?

Answer 6

A photon is a quantum of electromagnetic radiation, essentially the fundamental particle or “packet” of light and other forms of electromagnetic energy.

It is the smallest unit of energy that can be transported in the form of electromagnetic waves, including visible light, radio waves, X-rays, gamma rays, and more.

Question 7

What did Max Planck discover about the ultraviolet catastrophe?

Answer 7

The ultraviolet catastrophe was resolved in 1900 by Max Planck, who introduced a completely new way of thinking about the nature of radiation. Planck’s solution involved abandoning classical assumptions and adopting the idea that energy is quantized.

Planck proposed that the energy of oscillators (which he considered to be the source of the radiation) is quantized, meaning that energy can only be emitted or absorbed in discrete packets, or quanta, rather than continuously. This idea led to the famous Planck’s radiation law.

What if light could be emitted only at discrete wavelengths or intensities? What if, instead of light being released as a continuous stream of energy, it was released in discrete little packages—predictably sized bursts of electromagnetic energy? These packets of energy were described by Planck as quanta (singular: quantum) and the field of quantum mechanics was born.

Question 8

What did Henry Moseley discover about protons and neutrons?

Answer 8

Henry Moseley made a groundbreaking contribution to our understanding of the ATOMIC STRUCTURE through his discovery of the relationship between an element’s ATOMIC NUMBER and its position in the periodic table. Moseley’s work provided essential insights into the nature of PROTONS and helped clarify the concept of atomic numbers, although his research did not directly involve neutrons.

Question 9

What did James Chadwick discover about protons and neutrons?

Answer 9

James Chadwick is best known for his discovery of the NEUTRON in 1932, which had profound implications for our understanding of atomic structure.

Question 10

Who discovered the proton and the nucleus?

Answer 10

The proton was discovered by the British physicist Ernest Rutherford in 1917. Ernest Rutherford is credited with the discovery of the nucleus in 1911, following his gold foil experiment.

Question 11

How do excited state and ground state make light?

Answer 11

When a current is passed through a gas at low pressure, the potential energy of some of the gas atoms increases in what is called the excited state. The lowest energy state of an atom is its ground state. When an excited atom returns to the ground state, it gives off EM radiation in the form of coloured lights. When that light is passed through a prism, it is separated into specific wavelengths of visible light.

Question 12

Who discovered wave-particle duality of nature?

Answer 12

Louis de Broglie

Wave-particle duality is one of the key principles of quantum mechanics, which suggests that every particle or quantum entity, such as an electron or photon, exhibits both wave-like and particle-like properties, depending on how it is observed.

Question 13

Standing wave is?

Answer 13

A standing wave has a wavelength that when multiplied by any integer, equals the circumference of a Bohr’s orbit and connects the de Broglie wavelength to the Bohr orbital radius.

Question 14

Constructive interference is?

Answer 14

Constructive interference is a phenomenon that occurs when two or more waves combine in such a way that their amplitudes (the height or strength of the wave) add together, resulting in a wave with a greater amplitude. This occurs when the waves are in phase, meaning their crests and troughs align.

Question 15

Destructive interference is?

Answer 15

Destructive interference is the opposite of constructive interference. It occurs when two or more waves meet in such a way that their amplitudes cancel each other out, resulting in a reduction or complete cancellation of the overall wave. This happens when the waves are out of phase, meaning the crest of one wave aligns with the trough of another.

Question 16

Heisenberg uncertainty principle is?

Answer 16

The Heisenberg Uncertainty Principle was formulated by Werner Heisenberg, a German physicist, in 1927.

The Heisenberg Uncertainty Principle is a fundamental concept in quantum mechanics that states there are inherent limits to how precisely we can know certain pairs of properties of a particle, such as its position and momentum, at the same time. More specifically, the principle asserts that the more precisely we try to measure one of these properties, the less precisely we can know the other.

Question 17

Schrödinger’s Model: electron probability density is?

Answer 17

Electron probability density refers to the likelihood or probability of finding an electron in a particular region of space around an atom or molecule at a given time.

Question 18

Orbitals are?

Answer 18

Orbitals are mathematical functions that describe the wave-like behavior of electrons in atoms. In quantum mechanics, an orbital represents a region in space where an electron is most likely to be found.

An orbital is a 3D region around the nucleus that indicates the likely location of of an electron.

Question 19

Describe quantum numbers.

Answer 19

In order to better describe orbitals, scientists use quantum numbers that specify the properties of atomic orbitals and the properties of electrons in orbitals. There are a total of four quantum numbers. Every electron in an atom has a specific, unique set of four quantum numbers. The first three quantum numbers indicate the main energy level, the shape, and the orientation of the orbitals. The last quantum number describes the state of the electron in a particular orbital.
1. Principal Quantum Number (n)
2. Angular Momentum Quantum Number (l)
3. Magnetic Quantum Number (m, or ml)
4. Spin Quantum Number (s or ms)

Question 20

What is Pauli Exclusion Principle?

Answer 20

In 1925, an Austrian physicist named Wolfgang Pauli expressed the importance of electron spin in determining electron structure. The Pauli exclusion principle states that no two electrons in the same atom can have the same four quantum numbers.

Question 21

Isoelectronic is?

Answer 21

Having an equal number of electrons or the same electron configuration.

Question 22

London Dispersion Forces are?

Question 23

Hydrogen bonds are?

Answer 23

Hydrogen bonds are about five times stronger than other dipole-dipole attractions.

Question 24

Dipole-dipole forces are?

Answer 24

Dipole-dipole forces are intermolecular forces that occur between molecules with permanent dipoles. A permanent dipole arises when there is a significant difference in electronegativity between the two atoms in a covalent bond, causing one end of the molecule to have a partial negative charge (δ-) and the other end to have a partial positive charge (δ+).

These forces arise because the positive end of one molecule is attracted to the negative end of a neighboring molecule, creating a force of attraction between them. This interaction is weaker than covalent or ionic bonds but is still significant in determining the physical properties of substances, such as boiling points, melting points, and solubility.

Question 25

What is net dipole?

Answer 25

The net dipole of a molecule refers to the overall dipole moment of the molecule, taking into account both the individual bond dipoles and the molecule’s geometry. It is a measure of the separation of positive and negative charge centers in the molecule. In simpler terms, it indicates whether a molecule has an overall polarity and how strongly that polarity exists.

Question 26

What’s a bond dipole?

Answer 26

A bond dipole refers to the separation of charge that occurs in a polar covalent bond due to a difference in electronegativity between the two atoms involved in the bond. It results in partial positive (𝛿+) and partial negative (𝛿−) charges on the atoms, which are attracted to each other.

Question 27

What are intramolecular forces?

Answer 27

Intramolecular forces are the forces that hold the atoms together within a molecule or compound. These forces are responsible for the chemical bonds between atoms, and they determine the structure and stability of molecules. Intramolecular forces are generally much stronger than intermolecular forces (which act between different molecules).

Question 28

What are intermolecular forces?

Answer 28

Intermolecular forces (IMFs) are the forces of attraction or repulsion that act between different molecules. Unlike intramolecular forces, which hold atoms together within a molecule, intermolecular forces operate between molecules and influence the physical properties of substances, such as boiling points, melting points, and solubility. IMFs are generally weaker than intramolecular forces, but they are still essential in determining how molecules behave in different states of matter (solid, liquid, gas).

Question 29

What is substitutional alloy?

Answer 29

A substitutional alloy is a type of alloy in which atoms of the original metal are replaced or “substituted” by atoms of a different element, typically another metal, that is similar in size and chemical properties. In this type of alloy, the atoms of the alloying element fit into the metal’s lattice structure by replacing some of the atoms of the base metal, creating a homogeneous mixture at the atomic level.

Question 30

What is an interstitial alloy?

Answer 30

An interstitial alloy is a type of metal alloy where the atoms of a smaller element occupy the interstitial spaces (the gaps) between the atoms of a larger element in the metal’s crystal lattice. Unlike substitutional alloys, where atoms of a different element replace atoms of the base metal in the lattice, interstitial alloys form when smaller atoms fit into the voids or “interstices” of the metal’s structure, creating a solid solution.

Question 31

Coordinate covalent bonds are?

Answer 31

A coordinate covalent bond (also called a dative bond) is a type of covalent bond in which both electrons that form the bond come from the same atom. In contrast to a typical covalent bond, where each atom contributes one electron to the bond, a coordinate covalent bond involves one atom donating a pair of electrons to form the bond, while the other atom accepts them.

Question 32

Duet rule is?

Answer 32

The Duet Rule is a special bonding rule applicable to hydrogen and helium, where these elements tend to form bonds that result in them having two electrons in their valence shell. This rule is important when understanding the bonding behavior of hydrogen and helium, as these elements do not follow the octet rule that applies to most other elements.

Question 33

Octet rule is?

Answer 33

The Octet Rule is a fundamental principle in chemistry that states that atoms tend to form bonds in such a way that they achieve eight electrons in their valence (outermost) shell. This gives the atom the same electron configuration as a noble gas, which is typically the most stable configuration for most elements. The rule is primarily used to explain how atoms bond in order to gain chemical stability, and it applies to most elements in the s- and p-block of the periodic table.

Question 34

Bonding pairs are?

Answer 34

Bonding pairs refer to pairs of electrons that are shared between two atoms in a covalent bond. These electrons are involved in holding the atoms together, forming a chemical bond. In a covalent bond, the bonding pair is the set of electrons that both atoms “share” to satisfy the valence shell electron configurations (such as the octet rule for most atoms) and achieve stability.

Question 35

Lone pairs are?

Answer 35

Lone pairs are pairs of electrons that are localized on a single atom in a molecule and are not involved in bonding with other atoms. These electrons are in the outermost electron shell (valence shell) of an atom and are not shared with other atoms to form a chemical bond. Lone pairs are important for understanding the shape, reactivity, and overall properties of molecules.

Question 36

Polar means?

Answer 36

In chemistry, the term polar refers to a molecule or bond in which there is an uneven distribution of charge due to differences in the electronegativity of the atoms involved, or the asymmetry of the molecule. A polar molecule or polar bond has regions with partial positive charges (δ+) and partial negative charges (δ−), creating a dipole. These charge separations occur because one atom in the bond “pulls” electrons more strongly than the other, creating an imbalance.

Question 37

Non-polar means?

Answer 37

Non-polar refers to a type of molecule or chemical bond where there is no significant separation of charge. In non-polar molecules or bonds, the electrons are shared equally (or nearly equally) between the atoms involved, resulting in no distinct positive or negative regions within the molecule. This lack of charge separation means that non-polar molecules do not have a dipole moment (a separation of charge).

Question 38

Non-polar covalent bonds are?

Answer 38

Non-polar covalent bonds are a type of chemical bond where two atoms share a pair of electrons equally or almost equally. This equal sharing occurs when the two atoms involved have very similar or identical electronegativities—meaning they have the same ability to attract electrons. As a result, the electron density is distributed symmetrically across the two atoms, and there is no significant separation of charge (no partial positive or partial negative charges).

Question 39

Polar covalent bonds are?

Answer 39

Polar covalent bonds are a type of chemical bond where two atoms share electrons unequally due to a difference in their electronegativities. The atom with the higher electronegativity attracts the shared electrons more strongly, resulting in a partial negative charge (δ−) on that atom and a partial positive charge (δ+) on the other atom. This creates an electrical dipole—a molecule or bond with distinct positive and negative ends.

Question 40

Ionic bonds are?

Answer 40

Ionic bonds are a type of chemical bond formed when electrons are transferred from one atom to another, resulting in the formation of ions—charged particles. This bond typically occurs between atoms with a large difference in electronegativity (typically greater than 1.7). In an ionic bond, one atom donates one or more electrons to another atom, which leads to the formation of positively charged ions (cations) and negatively charged ions (anions). The electrostatic attraction between the oppositely charged ions holds the atoms together in the ionic bond.

Question 41

Valence Shell Electron Pair Repulsion (VSEPR) model is?

Answer 41

The Valence Shell Electron Pair Repulsion (VSEPR) model is a theory used to predict the three-dimensional (3D) shapes or molecular geometries of molecules based on the number of electron pairs (both bonding and lone pairs) surrounding the central atom. According to the VSEPR model, electron pairs arrange themselves around the central atom in a way that minimizes electron-electron repulsion, resulting in the most stable arrangement.

The basic idea of the VSEPR theory is that electron pairs (whether they are in bonds or as lone pairs) repel each other, and the shape of the molecule will adjust so that these electron pairs are as far apart as possible.

Question 42

Wave mechanics is?

Answer 42

Wave mechanics is a branch of quantum mechanics that describes the behavior of particles, such as electrons, in terms of wave-like properties. It is based on the idea that particles can exhibit both particle-like and wave-like behavior, a concept known as wave-particle duality. This theory was developed to explain phenomena that classical mechanics and particle theory could not, particularly at the atomic and subatomic levels.

Question 43

Hybrid orbitals are?

Answer 43

It appears that when atoms form bonds, their simple atomic orbitals often mix to form new orbitals we call hybrid orbitals. These orbitals have unique shapes.

Question 44

sp hybrid orbitals are?

Answer 44

One kind of hybrid orbital occurs when an s orbital and a p orbital combine. This creates two new orbitals called sp hybrid orbitals. The label sp identifies the pure atomic orbitals the hybrid is formed from (one s and one p).

Question 45

Sigma (σ) bonds are?

Answer 45

Sigma (σ) bonds are a type of covalent bond formed by the head-on overlap of atomic orbitals. These bonds are the strongest type of covalent bond and are present in both single and multiple bonds between atoms. In a molecule, sigma bonds are the primary bonds that hold atoms together.

Question 46

Pi (π) bonds are?

Answer 46

Pi (π) bonds are a type of covalent bond that forms when two atomic orbitals overlap side-by-side (laterally) rather than head-on, as in sigma (σ) bonds. Pi bonds occur in molecules with multiple bonds, such as double or triple bonds, and they contribute to the overall bonding but are generally weaker than sigma bonds.

Question 47

sp2 hybrid orbitals are?

Answer 47

Another kind of hybrid orbital occurs when an s orbital and two p orbitals combine. This creates three new orbitals called sp2 hybrid orbitals. The label sp2 identifies the pure atomic orbitals the hybrid is formed from (one s and two p).

Question 48

sp3 hybrid orbitals are?

Answer 48

Another kind of hybrid orbital occurs when an s orbital and three p orbitals combine. This creates four new orbitals called sp3 hybrid orbitals. The label sp3 identifies the pure atomic orbitals the hybrid is formed from (one s and three p).