Particulate Nature Of Matter And Structure Of The Atom Flashcards
What is the dilution law?
It is the number of times a more concentrated solution is diluted to obtain a less concentrated solution
What is an atom?
The smallest particle of an element which can take part in a chemical reaction and retain its chemical properties
What is a molecule?
A chemically combined group of atoms which can take part in a chemical reaction and retain its original purpose
Define atomicity
The number of replaceable hydrogen ions in a compound
What is an ion?
An electrically charged atom formed by the loss or gain of one or more electrons
State 3 evidences of the Particulate Nature of Matter
Brownian motion
Osmosis
Crystallization
Diffusion
State 5 postulates of Dalton
Hint: TIDY AC
Tiny indivisible particles called atoms
Identical masses and sizes for the same element
Different elements have different masses and sizes
You can’t destroy or create atoms
Atoms combine is small whole number ratios
State 3 limitations of Dalton
Atoms are divisible into sub atomic particles what are protons, electrons and neutrons
Atoms can be physically destroyed or created in a chemical/nuclear fission or fussion reaction
Atoms of the same element can be different if they are isotopes
Describe Democritus’ theory of atoms.
Democritus proposed that all matter in the universe was made of tiny, indivisible solid objects called ‘atomos’.
What is the particulate nature of matter?
The particulate nature of matter is the idea that matter is made up of tiny particles such as atoms, molecules, or ions.
Explain the spread of potassium tetraoxomanganate (VII) crystals in water.
When a few crystals of KMnO4 are introduced into water, they fall apart and spread throughout the water, resulting in a uniform distribution of colored KMnO4.
How does ammonia gas spread in a laboratory?
Ammonia gas, or any strong perfume or substance with a strong scent, spreads among air particles to other parts of the laboratory.
What is crystallization and how does it provide evidence for the particulate nature of matter?
Crystallization is the process of forming a solid/crystal by combining millions of particles from a solution, demonstrating that matter consists of particles.
Define Brownian motion.
Brownian motion is the random movement of a speck of a solid on the surface of a liquid due to the random movement of the particles of the fluid.
Describe an atom.
An atom is the smallest particle of an element that can take part in a chemical reaction.
Define a molecule.
A molecule is the smallest, stable particle of an element or compound that consists of a single atom or a group of two or more atoms chemically combined.
What is the atomicity of calcium?
Calcium is monoatomic, meaning it consists of only one atom.
Describe a compound.
A compound is a substance that is formed from the chemical combination of atoms of two or more different elements in a fixed ratio or proportion.
What is the difference between a homogeneous and heterogeneous mixture?
A homogeneous mixture is uniform in composition throughout and normally in the same physical state, while a heterogeneous mixture’s composition is not uniform and may exist in different states.
Do noble gases exist as monoatomic or diatomic molecules?
Noble gases exist as monoatomic molecules.
Define an ion.
An ion is an electrically charged particle formed from an atom or compound by gaining or losing one or more electrons.
Describe a polyatomic ion.
A polyatomic ion is a group of bonded atoms with a charge.
What is the atomicity of oxygen molecule?
The atomicity of an oxygen molecule (O2) is diatomic, meaning it consists of two atoms.
Describe Dalton’s atomic theory.
Dal’s atomic theory proposed that matter is made up of small indivisible particles called atoms, which cannot be created or destroyed. Atoms of the same element are identical in size and mass, while atoms of different elements have different mass and size. Atoms combine to form compounds in simple whole numbers.
What is the law of conservation of mass?
The law of conservation of mass states that the mass of the starting materials in a chemical reaction is always equal to the mass of the ending materials.
Define alloys.
Alloys are mixtures of two or more metals, such as steel, that have properties different from those of the individual metals.
How do gas-gas mixtures differ from solid-liquid mixtures?
Gas-gas mixtures, like air, consist of gases uniformly mixed together, while solid-liquid mixtures, like salt solution, water, and sand, contain solid particles dispersed in a liquid.
What did Antoine Lavoisier observe in his experiments with metals?
Antoine Lavoisier observed that the mass of the starting materials in a reaction was always equal to the mass of the ending materials, leading to the law of conservation of mass.
Describe the law of definite proportions.
The law of definite proportions states that elements react in the same proportions by mass in every chemical reaction. For example, hydrogen and nitrogen react in a fixed ratio of 1:4.7 or 2:9.4.
What are sub-atomic particles?
Sub-atomic particles are smaller, more fundamental particles that make up atoms. Examples include protons, neutrons, and electrons
Why is Dalton’s theory of atoms considered incorrect?
Dalton’s theory is considered incorrect because it proposed that atoms are indivisible, when in fact they are composed of sub-atomic particles. Additionally, atoms can be created and destroyed in nuclear reactions.
Describe J.J. Thompson’s experiment to discover electrons.
J.J. Thompson used a cathode ray tube to observe cathode rays, which were deflected by electric and magnetic fields, indicating they were charged particles. He also found that the rays moved straight through the hole in the anode and were detected as a glow on a fluorescent screen.
What deductions did Thompson make from his observations of cathode rays?
Thompson deduced that the cathode rays were electric carriers, negatively charged, and present in all types of matter.
Define isotopes.
Isotopes are atoms of the same element that differ in mass and size.
How did Thompson describe the structure of an atom in his ‘plum pudding’ model?
Thompson proposed that an atom is a solid sphere of positive charge with negative electrons stuck uniformly in it, balancing the positive charges to make the atom neutral.
What is the charge to mass ratio of electrons according to Thompson’s measurements?
Thompson found that the charge to mass ratio of electrons is -1.7 × 10^8 C/g for all matter.
Do cathode rays behave differently when different gases, materials of the tube, and electrodes are changed?
No, cathode rays behave the same way regardless of the gases, materials of the tube, and electrodes used.
Describe Rutherford’s alpha particle scattering experiment.
Lord Rutherford bombarded thin foils of gold and other metals with alpha particles and observed that most of the particles passed through the foil without deviation, while a few were deflected through small and large angles, and very few bounced back.
What are alpha particles?
Alpha particles are ionized helium atoms emitted by radioactive substances or elements. They are heavier than electrons and easily ionize other particles.
Define Rutherford’s model of the atom.
Rutherford’s model states that the atom has a central nucleus, which contains positively charged protons and neutrons, and electrons orbit around the nucleus. The nucleus has most of the atom’s mass, despite occupying a small volume.
What is the significance of most alpha particles passing through the foil in Rutherford’s experiment?
It implies that most of the volume of the atom is empty space occupied by electrons, which are too light to deflect alpha particles.
Describe the observations made in Rutherford’s experiment.
Most alpha particles passed through the foil without deviation, a few were deflected through small and large angles, and very few bounced back.
How did Rutherford interpret the deflections of alpha particles in his experiment?
He deduced that the deflections were due to the repulsion of alpha particles by a concentrated region of positive charge in the atom.
Who discovered neutrons and how?
James Chadwick discovered neutrons in 1932 by bombarding a thin sheet of Beryllium with alpha particles, resulting in the emission of a high-energy radiation similar to gamma rays.
What is the relationship between the number of protons and electrons in a neutral atom?
In a neutral atom, the number of protons is equal to the number of electrons.
Define neutron number (N).
Neutron number (N) is the number of neutrons in the nucleus of an atom.
What are nucleons?
Nucleons are protons or neutrons in the nucleus of an atom.
Describe the mass number (A).
The mass number (A) is the sum of the number of protons and neutrons in an atom.
What is a nuclide?
A nuclide refers to a nuclear species with a known atomic and mass number.
Explain isotopy.
Isotopy is the phenomenon whereby atoms of the same element exist with different mass numbers.
What are isotopes?
Isotopes are atoms of the same element that have the same atomic number but different mass numbers due to the presence of a different number of neutrons.
Describe line spectrum.
A line spectrum a set of radiation of different frequencies separated from each other by dark spaces.
What is an emission spectrum?
An emission spectrum is obtained when an electron in its ground state absorbs energy, moves to a higher energy level called the excited state, and eventually falls back to its ground state, emitting energy as electromagnetic radiation of certain wavelengths. It appears as a series of bright lines separated by dark spaces.
How is an emission spectrum produced?
An emission spectrum is produced when gaseous hot atoms emit light as electrons travel between electrodes in a discharge tube. The emitted light is separated into its components by a transparent glass prism.
What are the characteristics of an emission spectrum?
The characteristics of an emission spectrum are that it is discrete and represents different energy levels, frequencies, or wavelengths. Each element has a unique emission spectrum, which is used in chemical analysis to identify unknown atoms.
List three uses of emission spectrum.
- Studying the composition of stars 2. Identifying elements (each element has a unique emission spectrum) 3. Creating decorative lights
Define absorption spectrum.
An absorption spectrum is formed when light passes through a cold gas (atomic vapors) and atoms in the gas absorb light energy at characteristic frequencies. The absorbed photons appear as black lines, as they have been absorbed and do not show up.
Define a quantum.
A quantum is the smallest quantity of energy that can be absorbed or emitted in the form of electromagnetic radiation when an electron makes a transition from one level to the next level.
Describe the convergence limit in the hydrogen emission spectrum.
The convergence limit is the frequency at which line spectra merge or where lines with increasing frequencies merge. It can be used to determine ionization energy.
What is a photon?
A photon is a quantum of electromagnetic radiation.
What is the formula to calculate the energy absorbed or emitted in a transition in the hydrogen atom?
The formula is ∆E=HV.
Explain Bohr’s theory in relation to the atomic spectra of hydrogen atom and hydrogen-like species.
Bohr’s theory provides an explanation of the atomic spectra of hydrogen atom and hydrogen-like species. It explains the simultaneous appearance of a large number of spectra lines in the spectrum of hydrogen by varying the values of the initial energy level (excited state) ni and the final (ground state) nf.
What is the Lyman series in the hydrogen emission spectrum?
The Lyman series arises when an electron moves to the n=1 orbit from any other orbits. It gives a series of lines in the ultraviolet region of the electromagnetic spectrum.
Describe the Balmer series in the hydrogen emission spectrum.
The Balmer series arises when an electron moves from ni=3,4,5,6 or 7 to nf=2. It gives a series of lines in the visible region of the electromagnetic spectrum.
Describe the Bohr planetary model of the atom.
The Bohr planetary model of the atom proposed that electrons exist and move in set circular orbits or energy levels around the nucleus at fixed distances from each other.
What was the main problem with Rutherford’s theory of the atom?
The main problem with Rutherford’s theory was that it couldn’t explain why an atom doesn’t collapse or the stability of the atom.
Define stationary states in the context of Bohr’s model of the atom.
Stationary states in Bohr’s model refer to the definite paths or energy levels in which electrons can move without losing energy.
How does an electron emit or absorb energy in Bohr’s model?
When an electron moves from one energy level to another in Bohr’s model, it emits or absorbs energy.
Describe the wave-particle duality.
Wave-particle duality refers to the ability of particles in motion to behave like waves and the ability of waves to behave like particles.
What is Heisenberg’s uncertainty principle?
Heisenberg’s uncertainty principle states that it is impossible to accurately measure both the momentum and position of an electron at the same time.
How did Schrödinger contribute to the understanding of the uncertainty principle?
Schrödinger suggested that the hydrogen atom can be described with a wave equation, which led to the concept of orbitals and the probability of finding an electron in a given volume of space.
Describe the principal quantum number (n).
The principal quantum number defines the main energy of the shells and their sizes. It can be any positive integer and determines the average distance of the electron from the nucleus.
What is the role of the angular momentum quantum number (l)?
The angular momentum quantum number determines the shape and type of the orbital occupied by the electron. It ranges from 0 to (n-1) and is denoted by letters such as s, p, d, f.
Define the magnetic quantum number (ml).
The magnetic quantum number describes the orientation of orbitals in space in the presence of an external magnetic field.
How are shells divided into subshells?
Shells are divided into subshells or sublevels, which are orbitals with the same angular momentum quantum number (l).
Do higher values of the principal quantum number (n) result in higher or lower energy electrons?
Higher values of the principal quantum number result in higher energy electrons and greater average distance from the nucleus.
Describe the relationship between the principal quantum number (n) and the energy level of a shell.
The principal quantum number determines the energy level of a shell. The main shells of an atom are labeled K, L, M, N, O, P, corresponding to the numbers 1, 2, 3, 4, 5, 6, etc.
What is the orbital designation for the subshell with l=2 when n=4?
The orbital designation for the subshell with l=2 when n=4 is 4d.
Describe the observation in experiments when an atom is placed in a field.
Additional lines appear in its spectra.
Who provided the explanation for the splitting of a single spectra line of the hydrogen atom in the presence of an external electric field?
Lande.
What is the purpose of the magnetic Quantum Number?
To specify the further divisions of sub shells or energy sublevels.
How is the number of ml values determined for a given value of l?
By using the formula 2l+1.
Describe an atomic orbital.
An atomic orbital is a region or volume of space around the nucleus in a principal energy level where there is a high probability of finding a specified electron.
What is the maximum number of electrons that can be accommodated in a subshell with principal quantum number n=3?
The maximum number of electrons that can be accommodated in a subshell with n=3 is 9.
Define a shell in terms of atomic orbitals.
A shell, also known as a principal level, is a collection of orbitals with the same principal quantum number.
How many subshells are there in the energy level with principal quantum number n=4?
There are 4 subshells in the energy level with n=4.
Describe the shape of a p-orbital.
The p-orbital has a dumbbell shape.
What is the probability of finding an electron in each half of a p-orbital?
An electron in a p-orbital has an equal probability of being found in each half.
How are the three p-orbitals oriented in space?
The three p-orbitals are perpendicular to each other and directed towards the x, y, and z axes.
Define a nodal plane in an orbital.
A nodal plane is an area within an orbital where the probability of finding an electron is zero.
List the five degenerate orbitals in the d-shell.
The five degenerate orbitals in the d-shell are dxy, dxz, dyz, dx2-y2, and 3dz2.
What does Aufbau’s Principle state?
Aufbau’s Principle states that orbitals of lower energies are filled with electrons first before orbitals of higher energies
What is Pauli’s Exclusion Principle?
Pauli’s Exclusion Principle states that the total number of electrons that can fill any one orbital must be two and they must have opposite spins.
Describe the three main methods of writing electronic configuration using orbitals.
The three main methods are: 1) Electron-in-boxes method, 2) Using the notation, and 3) Using the noble gases.
What is the reason for using fully filled or half filled orbitals in electronic configuration?
The reason is that there is extra stability associated with atoms with fully filled orbitals as well as half filled orbitals.
Define the s-block in the periodic table.
The s-block in the periodic table consists of elements in group I and II. All elements in this block have their last (outermost) electrons entering the s-orbital, which can hold a maximum of two electrons.
How many elements are present in the d-block of the periodic table?
There are 10 elements in the d-block of the periodic table. Their valence electrons enter into the d-orbital, which can hold a maximum of 10 electrons.
What is Hund’s Rule of Maximum Multiplicity?
It states that, degenerate orbitals (orbitals of the same energy) are first filled with single
electrons with parallel spins before pairing up begins with opposite spins.
