2A1 Atomic and Subatomic Structures Flashcards
Explore the atomic and subatomic structure through an understanding of models and atomic components.
Define:
Atom
The smallest unit of matter that retains the properties of an element and serves as the building block of all substances in the universe.
## Footnote
‘Atom’ derives from a Greek word meaning ‘indivisible’.
What is the atomic structure?
It refers to the arrangement of protons, neutrons, and electrons in an atom.
Protons and neutrons form the nucleus, while electrons orbit around it. Atomic structure also determines the atom’s chemical and physical properties.
Explain the difference between an atom and a molecule.
- An atom is the smallest unit of an element.
- A molecule is a group of two or more atoms chemically bonded together.
True or false:
All atoms of the same element have the same number of protons.
True
The number of protons, called the atomic number, identifies the element.
Fill in the blank:
Protons and neutrons are found in the _______ of an atom.
nucleus
The nucleus accounts for nearly all the atom’s mass.
What is the net charge of a neutral atom?
Zero
The positive charges of protons and the negative charges of electrons balance each other.
True or false:
The nucleus of an atom carries a positive charge.
True
This is due to the presence of positively charged protons.
Define:
Isotopes
Atoms of the same element that have the same number of protons but different numbers of neutrons, leading to variations in atomic mass.
Isotopes can have varying stability and are used in applications like radiocarbon dating.
True or false:
Atoms of the same element always have the same number of neutrons.
False
Atoms of the same element can have different number of neutrons, forming isotopes. Isotopes share chemical properties but differ in mass.
How many elements are known to exist?
118 different elements
Around 92 occur naturally and 26 are created in laboratories.
The number of created elements may fluctuate as new elements are discovered.
What information does the Periodic Table of Elements provide?
It organizes all known elements based on their atomic number, electron configuration, and chemical properties, revealing periodic trends.
Each element is composed entirely of one type of atom.
What is the standard unit for quantifying the amount of substance in chemistry?
Mole
One mole is equal to 6.02 X 10^23 atoms.
What does the term atomic mass unit (amu) refer to?
It is a unit of mass used to express atomic and molecular weights.
An atomic mass unit (amu) is a unit of mass defined as one-twelfth the mass of a carbon-12 atom.
True or false:
Neutrons have no mass.
False
Neutrons have a mass similar to that of protons. They both contribute to the atom’s mass.
Fill in the blank:
Atoms bond together to form ________.
molecules
These molecules, including compounds, have unique properties and include everything from water to complex biological structures.
Fill in the blank:
Electrons are located in the _______ surrounding the nucleus of an atom.
Electron shells or orbitals.
These regions determine the atom’s chemical properties.
How are quarks related to protons and neutrons?
Protons and neutrons are composed of three quarks each.
## Footnote
Quarks are elementary particles held together by the strong force. A proton consists of two up quarks and one down quark, while a neutron consists of two down quarks and one up quark.
What is the mass of an electron compared to a proton?
An electron’s mass is about 1/1836th that of a proton.
This small mass makes electrons negligible when calculating atomic mass.
Fill in the blanks:
The atomic mass of an atom is primarily determined by the number of _______ and _______.
protons; neutrons
Electrons have negligible mass and don’t significantly affect atomic mass.
Why are electrons important in chemical reactions?
Electrons participate in forming bonds between atoms.
Their arrangement in orbitals determines reactivity.
True or false:
Protons determine the chemical reactivity of an atom.
False
Protons define the element, but electron arrangement dictates reactions.
Define:
Valence electrons
The electrons in the outermost shell of an atom.
They determine how atoms interact and bond with others.
Fill in the blank:
John Dalton’s atomic model is called the ________, which describes atoms as indivisible particles.
solid sphere model
Dalton developed this model in 1803 based on his experiments with gases.
Fill in the blanks:
According to Dalton’s atomic theory, atoms cannot be ________ or ________.
created; destroyed
Dalton also stated that all atoms of a pure element are identical.
What was the main limitation of Dalton’s model of the atom?
It failed to account for the existence of subatomic particles.
This model couldn’t explain phenomena like electrical conductivity or radioactive decay.
What is the plum pudding model?
An atomic structure model that describes an atom as a positively charged sphere with negatively charged electrons embedded throughout, resembling raisins in a pudding.
This model was proposed by J.J. Thomson.
True or false:
The plum pudding model accurately explained the distribution of positive and negative charges in the atom.
False
Rutherford’s gold foil experiment demonstrated that most of the atom is empty space, disproving the idea of a uniform positive charge.
What key discovery did Ernest Rutherford make from his gold foil experiment?
The nucleus of the atom.
Rutherford’s experiments showed that atoms have a dense center (nucleus) with electrons orbiting around it.
Fill in the blank:
A limitation of Rutherford’s model was that it couldn’t explain why _______ do not lose energy and collapse into the nucleus due to electrostatic attraction.
electrons
According to classical physics, orbiting electrons would lose energy and collapse into the nucleus, which doesn’t happen in reality.
What key idea did Niels Bohr introduce in his atomic model?
Electrons orbit the nucleus in specific energy levels.
These orbits are quantized, meaning electrons can only exist in specific energy levels, not between them.
True or false:
According to the Bohr model, electrons can occupy positions between discrete energy levels.
False
Electrons transition between energy levels by absorbing or emitting energy in discrete amounts.
What experimental evidence supported Bohr’s atomic model?
The hydrogen emission spectrum experiment.
This experiment showed distinct spectral lines, which the Bohr model successfully explained.
What are the limitations of the Bohr model?
It accurately describes hydrogen-like atoms (single-electron systems) but fails for multi-electron atoms.
This failure is because the Bohr model does not account for electron-electron interactions or the effects of quantum mechanics.
How did Bohr’s model influence future atomic models?
It laid the groundwork for quantum mechanics.
Bohr’s introduction of quantized energy levels was a pivotal step toward modern atomic theory.
Define:
Photon
A particle of light emitted or absorbed during electron transitions.
Photons carry energy equal to the difference between the initial and final energy levels of the electron.
Fill in the blank:
When an electron moves to a lower energy level, it ____ a photon.
emits
The energy of the photon corresponds to the energy difference between the two levels.
What atomic model did Erwin Schrödinger develop?
The quantum model.
Also known as the electron cloud model.
This model predicts the probability of finding an electron in certain areas around the nucleus.
Why is the quantum mechanical model more complex to understand than earlier models?
It describes electrons as probability clouds rather than fixed orbits.
This model relies on abstract mathematics, like wave functions, which can be challenging for beginners.
Fill in the blank:
The Bohr atomic model includes the notion that electrons orbit a fixed nucleus with _____ _____ ______ _______.
quantized orbital angular momentum.
This leads to discrete energy states.
What is the quantization formula for angular momentum in the Bohr model?
L = nℏ
Where L is angular momentum, n is a quantum number, and ℏ is the reduced Planck’s constant.
What determines the frequency of radiation emitted when an electron transitions between energy levels in the Bohr model?
By the energy difference between the initial and final energy levels, given by ΔE = hƒ, where h is Planck’s constant and ƒ is the frequency.
This principle is a cornerstone of quantum mechanics, demonstrating that energy is quantized and transitions involve discrete energy packets (photons).
What is the significance of the Coulomb force in the Bohr model?
It acts as the centripetal force that keeps electrons in circular orbits around the nucleus.
## Footnote
It balances the attractive force between the negatively charged electron and the positively charged nucleus. The force is proportional to the product of the charges and inversely proportional to the square of the distance.
Define:
Electron configuration
The arrangement of electrons in an atom’s orbitals, following specific rules.
Electron configuration helps predict an element’s chemical properties and behavior.
Fill in the blank:
The Aufbau principle states that electrons fill the _______ energy orbitals first.
lowest
This principle ensures that the atom’s total energy is minimized.
True or false:
In electron configuration, orbitals within the same subshell are always filled with paired electrons before being singly occupied.
False
According to Hund’s rule, electrons fill orbitals singly with the same spin before pairing up.
Define:
Spin
A quantum property of electrons that represents their intrinsic angular momentum.
It is quantized and can have values of +½ (‘up’) or -½ (‘down’). Spin determines how electrons pair up in orbitals and influences magnetic properties.
Fill in the blank:
The ________ _______ principle explains why two electrons in the same orbital must have opposite spins.
Pauli exclusion
This rule helps organize electrons in atoms and explains their unique arrangements.
What does the angular momentum quantum number (ℓ) describe in an atom?
The shape of an atomic orbital, categorizing it into s, p, d, or f orbitals.
It’s represented by letters: 0 is ‘s’, 1 is ‘p’, and 2 is ‘d’.
Why is it important to study atomic models?
They help us understand the structure and behavior of matter, including chemical reactions and physical properties.
Each model builds upon previous ones, refining our understanding of the atom.
How does studying subatomic particles contribute to advancements in science?
It leads to discoveries in fields like chemistry, physics, and medicine, including innovations like nuclear energy and medical imaging.
Knowledge of protons, neutrons, and electrons is foundational to modern science and technology.
