Atomic Theory of Matter
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Questions and Answers

What did Ernest Rutherford use to probe atomic structure?

  • Alpha particles (correct)
  • Neutrons
  • Beta particles
  • Gamma rays

    • What was observed when alpha particles were shot at the gold foil?

  • Most particles passed through with little deflection. (correct)
  • All particles bounced back.
  • Most particles were deflected at large angles.
  • All particles were absorbed.

    • From Rutherford's experiment, what did he conclude about the atom's positive charge?

  • It is spread evenly throughout the atom.
  • It is concentrated in the nucleus. (correct)
  • It is equal to the mass of the electrons.
  • It is located in the electron cloud.

    • What is the charge on the particles that form the beam of beta particles?

    <p>–1, because the beam consists of beta particles.</p> Signup and view all the answers

    What is the approximate diameter of the nucleus in units of pm?

    <p>100 pm</p> Signup and view all the answers

    What is the mass of a proton compared to an electron?

    <p>About 1840 times the mass of an electron.</p> Signup and view all the answers

    What particles are found in the nucleus of an atom?

    <p>Protons and neutrons</p> Signup and view all the answers

    What does Rutherford's model of the atom suggest about its structure?

    <p>Atoms are mostly empty space.</p> Signup and view all the answers

    What is the typical radius of an atomic nucleus?

    <p>5 x 10-3 pm</p> Signup and view all the answers

    Which subatomic particle has a charge of +1?

    <p>Proton</p> Signup and view all the answers

    What charge do protons have?

    <p>Positive</p> Signup and view all the answers

    What unit is used as the base unit for atomic mass?

    <p>Atomic mass unit (amu)</p> Signup and view all the answers

    Which of the following statements is true about neutrons?

    <p>They have a mass comparable to protons.</p> Signup and view all the answers

    Why did some alpha particles experience a large deflection during Rutherford's experiment?

    <p>They came near or directly at the nucleus.</p> Signup and view all the answers

    Atoms of the same element have the same number of which type of subatomic particle?

    <p>Protons</p> Signup and view all the answers

    What is measured in a mass spectrometer?

    <p>Atomic and molecular weight</p> Signup and view all the answers

    Who is the scientist associated with the reemergence of atomic theory in the early nineteenth century?

    <p>John Dalton</p> Signup and view all the answers

    What fundamental claim does Dalton's first postulate make about elements?

    <p>Elements are composed of extremely small particles called atoms.</p> Signup and view all the answers

    According to Dalton, how do atoms of different elements compare?

    <p>They differ in both mass and properties.</p> Signup and view all the answers

    What does the Law of Conservation of Mass state?

    <p>The total mass remains the same before and after a chemical process.</p> Signup and view all the answers

    What is the main idea behind Dalton’s fourth postulate regarding compounds?

    <p>A given compound always has the same number and kind of atoms.</p> Signup and view all the answers

    Proust's Law of Definite Proportions asserts that samples of a compound will have:

    <p>The same relative proportion of elements by mass.</p> Signup and view all the answers

    Which statement about chemical reactions is true according to Dalton's theory?

    <p>Atoms are neither created nor destroyed.</p> Signup and view all the answers

    What defines isotopes of the same element?

    <p>Different masses due to varying numbers of neutrons</p> Signup and view all the answers

    If the ratio of the masses of different elements in a compound is fixed, what can also be inferred?

    <p>The ratio of the atoms of these elements must also be constant.</p> Signup and view all the answers

    What is the atomic number (Z) of oxygen?

    <p>8</p> Signup and view all the answers

    Where are protons located in an atom?

    <p>In the nucleus</p> Signup and view all the answers

    What is the charge of a neutron?

    <p>No charge</p> Signup and view all the answers

    What does the atomic number represent?

    <p>The number of protons in an atom</p> Signup and view all the answers

    What is the mass number of an atom calculated from?

    <h1>of protons + # of neutrons</h1> Signup and view all the answers

    How do electrons occupy shells around the nucleus of an atom?

    <p>Only a limited number can fit in each shell, determined by the formula 2n^2</p> Signup and view all the answers

    Which statement about elements is true?

    <p>Elements are made up of atoms and are the building blocks of matter</p> Signup and view all the answers

    What are valence electrons?

    <p>Electrons in the outermost shell of an element</p> Signup and view all the answers

    In the Bohr Model, what represents the protons and neutrons?

    <p>They are located in the nucleus, shown as either plus signs or blank circles</p> Signup and view all the answers

    How are atoms primarily organized in the periodic table?

    <p>By atomic number</p> Signup and view all the answers

    Which particle orbits the nucleus of an atom?

    <p>Electrons</p> Signup and view all the answers

    Which of the following statements about atomic mass is correct?

    <p>It is the sum of the total number of protons and neutrons</p> Signup and view all the answers

    Study Notes

    Atomic Theory of Matter

    • Atoms are the fundamental building blocks of matter, reintroduced by John Dalton in the early 19th century.
    • Dalton proposed that each element is made of indivisible atoms that are identical in mass and properties.
    • Chemical reactions rearrange atoms; they are neither created nor destroyed, adhering to the Law of Conservation of Mass.
    • Dalton's fourth postulate states that atoms of different elements combine to form compounds in fixed ratios, supported by Proust's Law of Definite Proportions.

    Discovery of the Nucleus

    • Ernest Rutherford conducted a famous gold foil experiment where alpha particles were shot at thin metal foils to probe atomic structure.
    • Most alpha particles passed through with little deflection, indicating that atoms are mostly empty space.
    • Large-angle deflections suggested a dense, positively charged nucleus, composed of protons, at the center of the atom.

    Structure of the Atom

    • Protons have a positive charge, while electrons carry a negative charge; neutrons are neutral.
    • Protons and neutrons have similar masses, while electrons have negligible mass compared to them.
    • The atomic nucleus is where protons and neutrons reside, and the typical atomic radius is about 100 picometers (pm), with the nucleus being significantly smaller at about 5 x 10^-3 pm.

    Atomic Mass and Weight

    • Atomic mass is extremely small, with the heaviest known atoms weighing approximately 4 x 10^-22 g.
    • The atomic mass unit (amu) is the standard for measuring atomic masses, where 1 amu = 1.66054 × 10^-24 g.

    Isotopes

    • Isotopes are variants of the same element that differ in neutron count, hence differing in mass while maintaining the same number of protons.
    • Atomic number (Z) represents the number of protons in the nucleus and determines the element.

    Elements and the Periodic Table

    • Elements consist of specific atoms and are denoted by one or two-letter symbols, such as "O" for oxygen.
    • The periodic table organized elements based on atomic number, symbol, and average atomic mass, serving as a reference for all chemical elements.

    Atom Models

    • The Bohr Model depicts electrons in distinct orbits around the nucleus and shows protons and neutrons in the nucleus.
    • Electrons occupy energy levels or shells, with specific limits on how many electrons can exist in each shell, following the formula 2n^2.

    Valence Electrons

    • Electrons in the outermost shell are referred to as valence electrons and play a crucial role in chemical bonding and reactivity.

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    Related Documents

    Elements and Atoms Lecture 2024 PDF

    Description

    Explore the foundational concepts of the atomic theory that describes atoms as the fundamental building blocks of matter. This quiz highlights the postulates introduced by John Dalton in the early nineteenth century, which reshaped our understanding of elements and their compositions.

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