Chemistry Unit 1.2: Elements and Atoms
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Questions and Answers

What was the main conclusion of Rutherford's gold foil experiment?

  • The nucleus contains both protons and neutrons.
  • Atoms are mostly empty space with a small, dense, positively charged nucleus. (correct)
  • Atoms are solid spheres with electrons embedded throughout.
  • Electrons orbit the nucleus in specific energy levels.

Which of the following was NOT directly observed by Rutherford in his gold foil experiment?

  • Alpha particles were repelled and deflected backwards.
  • The nucleus contains neutrons. (correct)
  • Alpha particles were deflected at various angles.
  • Some alpha particles passed straight through the gold foil.

What evidence led Chadwick to conclude that the nucleus contains neutrons?

  • The observation that electrons orbit the nucleus in specific energy levels.
  • The observation that the masses of nuclei were not the same as the sum of the masses of protons. (correct)
  • The observation that alpha particles were deflected at various angles.
  • The observation that atoms emit certain colors of light.

What occurs when an electron jumps from a higher energy level to a lower energy level?

<p>The electron emits a burst of light energy. (D)</p> Signup and view all the answers

What is the outermost energy level of an atom called?

<p>The valence shell. (C)</p> Signup and view all the answers

What is the primary function of Bohr-Rutherford diagrams?

<p>To illustrate the structure of the atom, including the arrangement of electrons. (C)</p> Signup and view all the answers

Which of the following statements is TRUE about Bohr's model of the atom?

<p>It provides a simple and useful representation of electron energy levels. (B)</p> Signup and view all the answers

Which scientist's work led to the understanding that electrons exist in specific energy levels?

<p>Bohr (A)</p> Signup and view all the answers

What determines the identity of an element?

<p>The number of protons (A)</p> Signup and view all the answers

Which of the following is NOT a nuclear particle?

<p>Electron (A)</p> Signup and view all the answers

What is the neutron number (N) of an atom with an atomic number (Z) of 8 and mass number (A) of 16?

<p>8 (D)</p> Signup and view all the answers

Which isotope of carbon is the standard used for comparing atomic masses?

<p>Carbon-12 (B)</p> Signup and view all the answers

What is the function of a mass spectrometer?

<p>To measure the mass and abundance of isotopes (B)</p> Signup and view all the answers

Which type of radiation is most likely to penetrate deep into body tissue?

<p>Gamma rays (B)</p> Signup and view all the answers

What element is the radioactive noble gas that can accumulate in homes and contribute to lung cancer risk?

<p>Radon (C)</p> Signup and view all the answers

Whose law of triads organized elements into groups of three with similar properties?

<p>Dobereiner (D)</p> Signup and view all the answers

Which of these is NOT a common characteristic of radioactive isotopes?

<p>They are always found in nature (B)</p> Signup and view all the answers

What is the difference between alpha radiation and beta radiation?

<p>Alpha particles carry a positive charge, while beta particles carry a negative charge. (D)</p> Signup and view all the answers

Which of these options is NOT a reason why periodic trends occur?

<p>Electron-Electron Repulsion (A)</p> Signup and view all the answers

Which of the following best describes the effect of shielding on the effective nuclear charge?

<p>Shielding decreases the effective nuclear charge. (C)</p> Signup and view all the answers

What is the relationship between the number of protons in an atom and the nuclear charge?

<p>The number of protons is directly proportional to the nuclear charge. (C)</p> Signup and view all the answers

Which of the following statements is true for elements in the same period?

<p>Elements in the same period have the same number of electron shells. (B)</p> Signup and view all the answers

Why are Li, Na, and K in the same group on the periodic table?

<p>They have the same number of valence electrons. (A)</p> Signup and view all the answers

What is the relationship between the position of an element on the periodic table and its electron configuration?

<p>The period number indicates the number of energy levels in the electron configuration. (C)</p> Signup and view all the answers

Which of these is NOT a factor that influences the effective nuclear charge experienced by an electron in an atom?

<p>The number of neutrons in the nucleus (C)</p> Signup and view all the answers

Which of the following is TRUE about trends in the periodic table?

<p>Going down a group, atomic size generally increases. (C)</p> Signup and view all the answers

What does Schrodinger's Quantum Mechanical Model not have regarding electrons?

<p>Defined paths for electron movement (A)</p> Signup and view all the answers

What is the maximum number of valence electrons that hydrogen and helium can have to achieve a stable octet?

<p>2 electrons (B)</p> Signup and view all the answers

What type of ion is formed when an atom loses one or more electrons?

<p>Cation (B)</p> Signup and view all the answers

Which group of elements generally has a stable arrangement of 8 valence electrons?

<p>Noble gases (B)</p> Signup and view all the answers

Which of the following represents a nonmetal ion that typically gains electrons?

<p>Chloride ion (Cl-) (C)</p> Signup and view all the answers

How can an atom achieve a stable electron arrangement according to the octet rule?

<p>By sharing, losing, or gaining electrons (C)</p> Signup and view all the answers

What is the predicted behavior of metals with respect to their valence electrons?

<p>They tend to lose electrons to form cations (C)</p> Signup and view all the answers

In a Bohr-Rutherford diagram, how should an ion be represented?

<p>With square brackets and the charge indicated (B)</p> Signup and view all the answers

What does the Cl– ion represent?

<p>A negatively charged ion (B)</p> Signup and view all the answers

What is the valence of an atom?

<p>The charge of an ion (B)</p> Signup and view all the answers

Which statement is true about multivalent elements?

<p>They have more than one possible valence (D)</p> Signup and view all the answers

How are isotopes of an element distinguished?

<p>By their mass number (A)</p> Signup and view all the answers

What characterizes a polyatomic ion?

<p>It acts as a single entity despite being composed of multiple atoms (B)</p> Signup and view all the answers

What role do protons play in an atom?

<p>They are responsible for the element's identity (D)</p> Signup and view all the answers

Electrons primarily determine which aspect of an atom?

<p>The chemical properties of an atom (C)</p> Signup and view all the answers

What is the significance of neutrons in isotopes?

<p>They provide stability to the nucleus and do not alter the element's identity (A)</p> Signup and view all the answers

Which of the following statements regarding the atomic radius of elements is TRUE?

<p>Atomic radius increases down a group, as the number of occupied energy levels increases, leading to a larger electron cloud. (D)</p> Signup and view all the answers

Which of the following statements best describes the trend in ionization energy (IE) across a period?

<p>IE increases across a period due to the increasing effective nuclear charge, making the outer electrons more difficult to remove. (B)</p> Signup and view all the answers

Which of the following correctly describes the relationship between electron affinity and atomic radius?

<p>Electron affinity increases with decreasing atomic radius because the attraction between the nucleus and the added electron increases. (B)</p> Signup and view all the answers

Why is the ionic radius of a cation smaller than that of its parent atom?

<p>Cations lose electrons, resulting in decreased electron-electron repulsion and a smaller electron cloud. (C)</p> Signup and view all the answers

Which of the following statements correctly describes the relationship between electronegativity and atomic radius?

<p>Electronegativity increases with decreasing atomic radius because the nucleus has a stronger attraction to the bonding electrons. (A)</p> Signup and view all the answers

Which of the following elements would have the highest ionization energy?

<p>Chlorine (Cl) (B)</p> Signup and view all the answers

Which of the following statements about electron affinity is FALSE?

<p>Electron affinity can be positive (energy is released) or negative (energy is absorbed). (B)</p> Signup and view all the answers

Which of the following statements correctly describes the relationship between electron affinity and ionization energy?

<p>Both ionization energy and electron affinity increase across a period, but decrease down a group. (B)</p> Signup and view all the answers

Which of the following elements has the highest electronegativity?

<p>Fluorine (F) (D)</p> Signup and view all the answers

A neutral atom gains an electron. What type of ion is formed?

<p>An anion (C)</p> Signup and view all the answers

Which of the following statements regarding ionization energy is FALSE?

<p>First ionization energy is always greater than second ionization energy. (D)</p> Signup and view all the answers

What is the main reason for the trend in electronegativity across a period?

<p>Decreasing atomic radius (D)</p> Signup and view all the answers

Which of the following elements would form the most stable anion?

<p>Chlorine (Cl) (A)</p> Signup and view all the answers

Which of the following ions has the smallest ionic radius?

<p>Al3+ (A)</p> Signup and view all the answers

Which of the following statements about the trends in ionization energy and electronegativity are TRUE?

<p>Both ionization energy and electronegativity increase across a period. (D)</p> Signup and view all the answers

Flashcards

Rutherford's Gold Foil Experiment

An experiment where positively charged alpha particles were fired at a thin sheet of gold foil to determine the structure of an atom.

Rutherford's Nuclear Model

Atoms are mostly empty space with a dense, positively charged nucleus at the center and negatively charged electrons orbiting at a distance.

Nucleus

The small, positively charged core of an atom, containing protons and neutrons.

Neutron

The neutral particle found within the nucleus of an atom. It has a mass similar to a proton.

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Bohr's Atomic Model

An experiment using hydrogen gas and light to determine that electrons occupy specific energy levels called orbits around the nucleus.

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Energy Level

The specific energy level or orbit occupied by electrons around the nucleus.

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Valence Shell

The outermost energy level of an atom, containing electrons that participate in bonding with other atoms.

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Valence Electron

An electron in the valence shell, responsible for chemical bond formation.

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Schrödinger's Quantum Mechanical Model

A model that describes the probability of finding an electron in a certain region of space. It doesn't define a specific orbital path like Bohr's model.

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Stable Octet

The arrangement of electrons where the outermost shell (valence shell) has 8 electrons (or 2 for hydrogen and helium).

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Octet Rule

A generalization stating that atoms tend to gain, lose, or share electrons to achieve a stable octet configuration.

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Ion

An atom that has gained or lost electrons, resulting in a net positive or negative charge.

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Cation

A positively charged ion formed by losing one or more electrons.

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Anion

A negatively charged ion formed by gaining one or more electrons.

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Emission Spectrum

The unique set of spectral lines emitted by an element when its electrons transition between energy levels.

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Spectral Lines

The specific wavelengths of light emitted or absorbed by an element, corresponding to the energy differences between electron energy levels.

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What is an anion?

A negatively charged ion formed by gaining one or more electrons.

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What is valence?

The number of electrons an atom gains, loses, or shares when forming a chemical bond.

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What is a multivalent atom?

An atom that can have more than one possible valence.

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What is a polyatomic ion?

An ion comprised of two or more atoms that act as a single charged entity.

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What is an isotope?

A form of an element with the same number of protons but a different number of neutrons.

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What is the nucleus?

The central part of an atom containing protons and neutrons.

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What are protons?

Positively charged particles found in the nucleus of an atom.

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What are electrons?

Negatively charged subatomic particles that orbit the nucleus.

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Atomic Number (Z)

The number of protons in an atom's nucleus, determining its chemical identity.

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Atomic Mass (A)

The sum of protons and neutrons in an atom's nucleus, representing its mass.

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Period

The horizontal rows in the Periodic Table, indicating the number of electron energy levels occupied in an atom.

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Group/Family

The vertical columns in the Periodic Table, grouping elements with similar chemical properties due to having the same number of valence electrons.

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Effective Nuclear Charge (ENC)

The force experienced by an outer electron due to the positively charged nucleus, reduced by inner electrons.

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Electron-Electron Repulsion

The repulsion between electrons within an atom, causing them to spread out and minimize their interaction.

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Mass Number (A)

The sum of protons and neutrons in an atom's nucleus. It represents the atom's mass.

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Neutron Number (N)

The number of neutrons in an atom's nucleus. It can be calculated by subtracting the atomic number from the mass number.

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Relative/Average Atomic Mass

The weighted average of the masses of all naturally occurring isotopes of an element. It takes into account their relative abundances and is compared to the mass of carbon-12.

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Atomic Mass Unit (u)

A unit of mass used to express the mass of atoms. It is defined as one-twelfth the mass of a carbon-12 atom.

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Isotopic Abundance

The percentage of a specific isotope in a sample of an element. Most elements exist as a mixture of isotopes.

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Mass Spectrometer

A device used to determine the mass and abundance of isotopes in a sample. It can also provide information about the structure of molecules.

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Radioisotope

An isotope with an unstable nucleus that emits radiation to reach a more stable state. These elements have atomic numbers greater than 20.

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Nuclear Radiation

Energy or small particles emitted from the nucleus of a radioisotope during decay. It includes alpha particles (α), beta particles (β), and gamma rays (γ).

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Atomic Radius

The distance from the center of an atom to the outer edge of its electron cloud, usually measured in picometers (pm).

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Ionization Energy (IE)

The strength of the attraction between the nucleus and the outermost electrons in an atom, measured by the energy required to remove an electron.

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Electron Affinity

The energy change that occurs when a neutral atom in the gaseous state gains an electron, often releasing energy.

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Electronegativity

A measure of an atom's ability to attract shared electrons in a covalent bond.

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Ionic Radius

The distance from the center of an ion to the outer edge of its electron cloud.

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Atomic Radius Trend: Down a Group

An increase in the atomic radius as you move down a group in the periodic table due to the addition of electron shells.

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Atomic Radius Trend: Across a Period

A decrease in the atomic radius as you move across a period in the periodic table due to a stronger attraction between the nucleus and electrons.

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Ionization Energy Trend: Across a Period

An increase in ionization energy as you move across a period in the periodic table. Atoms hold electrons more tightly due to a stronger nuclear pull.

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Ionization Energy Trend: Down a Group

A decrease in ionization energy as you move down a group in the periodic table. Outer electrons are further from the nucleus, easier to remove.

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Electron Affinity Trend: Across a Period

An increase in electron affinity as you move across a period in the periodic table. Atoms have a stronger attraction for incoming electrons.

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Electron Affinity Trend: Down a Group

A decrease in electron affinity as you move down a group in the periodic table. Atomic radius increases, weakening the attraction between the nucleus and incoming electrons.

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Electronegativity Trend: Across a Period

An increase in electronegativity as you move across a period in the periodic table. Strong nuclear charge pulls more strongly on shared electrons.

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Electronegativity Trend: Down a Group

A decrease in electronegativity as you move down a group in the periodic table. Increased distance and shielding weaken the attraction on shared electrons.

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Study Notes

Unit 1.2: Elements and Atoms

  • Element: A substance that cannot be broken down into simpler substances through a chemical reaction. All matter is composed of elements.
  • Atom: The smallest possible unit of an element. Greek for "not able to be cut."

Democritus and Aristotle

  • Democritus: Proposed the concept of "atomos" (uncuttable) atoms, different sizes, constant motion, and separated by empty space.
  • Aristotle: Proposed the "Four Element Model" (fire, air, earth, water), an idea that lasted for 2,000 years.

Alchemists

  • 1st - 17th Century: Explored matter intensely. Searched for the "elixir of life," philosopher's stone (to transform metals into gold). Developed lab glassware and chemical handling procedures. Discovered various elements (arsenic, antimony, bismuth, phosphorus).

Dalton's Billiard Ball Model (1808)

  • Experiment: Broke down water using electricity.
  • Observations: Hydrogen and oxygen gas were produced, with different properties from water.
  • Conclusion: Water is a compound. Matter is made of tiny, indivisible particles (atoms).
  • Atoms of the same element are identical in mass and size.
  • Atoms of different elements have different masses and sizes.
  • Compounds are formed when atoms of different elements combine in definite proportions.
  • Atoms cannot be created, destroyed, or divided in chemical reactions.

Thomson's Plum Pudding Model (1904)

  • Experiment: Cathode Ray Tube experiment.
  • Observations: A ray was produced starting from the negative electrode (cathode). The ray was repelled by a negatively charged pole.
  • Conclusion:
  • Atoms contain negatively charged particles (electrons).
  • Electrons are small and have negative charges.
  • Atoms are spheres of positive charge with negatively charged electrons embedded within.

Rutherford's Nuclear Model (1911)

  • Experiment: Alpha particles were fired at a thin gold foil.
  • Observations: Most particles passed straight through, but some were deflected at large angles, some bounced back.
  • Conclusion:
  • Atoms are mostly empty space.
  • Atoms contain a small, dense, positively charged nucleus.
  • Electrons orbit the nucleus at a distance.

Chadwick's Discovery (1932)

  • Experiment: Worked with Rutherford.
  • Observations: Observed differences in the mass of atomic nuclei.
  • Conclusion: Nuclei contain neutral particles called neutrons, along with positively charged protons.

Bohr's Planetary Model (1913)

  • Experiment: Applied electricity and thermal energy to hydrogen gas. Observed light through a prism.
  • Observations: Hydrogen atoms emitted light only at specific colors.
  • Conclusion: Electrons orbit the nucleus in specific energy levels. Each energy level can hold a certain number of electrons. Jumping from one level to another releases light.

Bohr-Rutherford Diagrams

  • Diagrams that show the number of subatomic particles (protons, neutrons, electrons) and their arrangement in atoms.

Schrodinger's Quantum Mechanical Model (1926)

  • Does not have well-defined orbits for electrons.
  • Describes electron position as a "cloud of probability."

Stable Octet

  • Electron arrangement where the valence shell is full with 8 valence electrons (2 for hydrogen and helium). This is true for the first 18 elements.

Ion

  • A charged atom formed when an atom gains or loses electrons.
  • Cations: Positively charged ions (metals).
  • Anions: Negatively charged ions (nonmetals).

Polyatomic Ions

  • Ions composed of more than one atom.

Subatomic Particles

  • Protons: Positively charged particles in the nucleus.
  • Neutrons: Neutral particles in the nucleus.
  • Electrons: Negatively charged particles orbiting the nucleus.

Isotopes

  • Atoms of the same element with different numbers of neutrons. They exhibit similar chemical properties, differing in some physical properties.

Standard Atomic Notation

  • A method to represent isotopes with atomic number and mass number.

Relative/Average Atomic Mass

  • The weighted average mass of all naturally occurring isotopes of an element.

Atomic Mass Unit

  • A unit of mass equal to 1/12 the mass of a carbon-12 atom.

Mass Spectrometer

  • An instrument that measures isotopic abundances.

Radioisotopes

  • Isotopes with unstable nuclei; they emit radiation to achieve a more stable state. This may have medical, energetic, or other applications.

Radiation Protection

  • Methods to protect against harmful effects of radiation.

Periodic Table

  • Organizes elements by increasing atomic number, with elements exhibiting similar properties in columns (groups).

Periodic Law

  • Physical properties repeat regularly as elements are arranged by increasing atomic number.
  • Patterns observed in properties of elements as you move across or down the periodic table (e.g., atomic radius, ionization energy, electronegativity).

Effective Nuclear Charge

  • The net positive charge experienced by an outer electron in an atom, which includes the attraction of positively charged protons and reduced attraction due to shielding by inner electrons.

Electron Affinity

  • The energy change that occurs when a neutral atom gains an electron.

Electronegativity

  • The relative ability of an atom to attract shared electrons in a covalent bond.

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Explore the fundamental concepts of elements and atoms in this quiz. Delve into the historical perspectives of Democritus and Aristotle, and discover the contributions of early alchemists and Dalton's experiments. Test your knowledge on the building blocks of matter!

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