Chemistry Chapter 3: Atoms and Matter
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Questions and Answers

How many protons are present in calcium-40?

  • 14
  • 18
  • 20 (correct)
  • 22

Given that Beaker A contains 2.06 mol of copper and Beaker B contains 222 grams of silver, which beaker contains the larger mass?

  • Cannot determine without molar masses
  • Beaker B (correct)
  • Both beakers contain equal mass
  • Beaker A

What is the hyphen notation for an isotope with a mass number of 28 and an atomic number of 14?

  • Calcium-28
  • Carbon-28
  • Neon-28
  • Silicon-28 (correct)

Which of the following isotopes contains more neutrons than protons?

<p>Calcium-40 (A)</p> Signup and view all the answers

If you wanted to convert 0.087 g of aluminum to milligrams, what would be the final result?

<p>87 mg (C)</p> Signup and view all the answers

What does the law of multiple proportions state about compounds composed of the same two elements?

<p>Their mass ratios are always small whole numbers. (C)</p> Signup and view all the answers

Which statement is NOT part of Dalton's atomic theory?

<p>Atoms can be created or destroyed in chemical reactions. (C)</p> Signup and view all the answers

What does Dalton’s atomic theory suggest about atoms of different elements?

<p>They differ in size, mass, and other properties. (D)</p> Signup and view all the answers

How does Dalton's atomic theory relate to the law of conservation of mass?

<p>It suggests that atoms are just rearranged in reactions. (D)</p> Signup and view all the answers

What is true regarding the formation of compounds according to Dalton's atomic theory?

<p>Compounds consist of atoms in whole-number ratios. (B)</p> Signup and view all the answers

Which best describes the atoms of an element, according to Dalton's theory?

<p>They are identical in mass and other properties. (D)</p> Signup and view all the answers

What can be inferred about chemical reactions based on Dalton's theory?

<p>Atoms are merely combined, separated, or rearranged. (A)</p> Signup and view all the answers

What is the average atomic mass of naturally occurring copper?

<p>63.546 u (B)</p> Signup and view all the answers

Which isotope has the highest natural abundance among the isotopes listed?

<p>Uranium-238 (C)</p> Signup and view all the answers

How is the average atomic mass of an element determined?

<p>Calculating based on the mass and relative abundance of isotopes (C)</p> Signup and view all the answers

What percentage of naturally occurring hydrogen is Hydrogen-1?

<p>99.9885% (C)</p> Signup and view all the answers

Which of the following isotopes has an atomic mass greater than its mass number?

<p>Oxygen-17 (C)</p> Signup and view all the answers

Which isotope of copper has a lower atomic mass?

<p>Copper-63 (D)</p> Signup and view all the answers

Which isotope has the smallest natural abundance percentage?

<p>Uranium-234 (A)</p> Signup and view all the answers

What is the average atomic mass of Hydrogen-2?

<p>2.014 102 u (B)</p> Signup and view all the answers

What is the correct average atomic mass for Carbon based on its isotopes?

<p>12.0107 u (B)</p> Signup and view all the answers

Which atomic mass represents an isotope with the highest natural abundance?

<p>238.050 784 u (B)</p> Signup and view all the answers

What is the charge of a proton?

<p>+1 (D)</p> Signup and view all the answers

Which particle has the least mass?

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

What unit is used to express atomic radii?

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

What is the approximate radius of a typical atom in picometers?

<p>40 to 270 pm (C)</p> Signup and view all the answers

How large are atomic nuclei compared to the entire atom?

<p>About 0.001 pm (A)</p> Signup and view all the answers

What is the electric charge of a neutron?

<p>0 (C)</p> Signup and view all the answers

What does the term 'electron cloud' refer to?

<p>The region where electrons are likely found (D)</p> Signup and view all the answers

Which of the following is true about the densities of atomic nuclei?

<p>They have incredibly high densities (C)</p> Signup and view all the answers

What does 1 picometer equal in meters?

<p>$1 imes 10^{-12}$ m (D)</p> Signup and view all the answers

What is the average atomic mass of an element based on?

<p>The weighted average of the atomic masses of its isotopes (C)</p> Signup and view all the answers

How do different samples of the same element vary in relation to isotopes?

<p>They can differ in the relative abundance of isotopes (D)</p> Signup and view all the answers

In the marble example, how is the average mass calculated?

<p>By calculating the total mass of each type and dividing by the total number (B)</p> Signup and view all the answers

If a sample contains 30% of isotopes with a mass of 4 g and 70% with a mass of 5 g, what is the weighted average mass?

<p>4.7 g (B)</p> Signup and view all the answers

What does the average atomic mass differ from, which is purely a count?

<p>Atomic number of the element (B)</p> Signup and view all the answers

In the context of isotopes, what does the term 'weighted average' imply?

<p>Different isotopes influence the average based on their abundance (C)</p> Signup and view all the answers

Why is the average atomic mass considered a statistical calculation?

<p>It is derived from a sample rather than a total count (A)</p> Signup and view all the answers

Which method simplifies calculating the weighted average in a mixture?

<p>Multiplying each mass by its percentage in decimal form and adding (B)</p> Signup and view all the answers

What approach is incorrect when calculating weighted average?

<p>Adding mass values without considering the quantity of each type (C)</p> Signup and view all the answers

Flashcards

Law of Multiple Proportions

If elements combine to form different compounds, the ratios of masses of one element combined with a fixed mass of the other element will be small whole numbers.

Dalton's Atomic Theory

A theory proposing that elements are made of atoms and chemical reactions involve the rearrangement of atoms in whole number ratios.

Atomic Theory Statement 1

All matter is composed of extremely small particles called atoms.

Atomic Theory Statement 2

Atoms of an element are identical and atoms of different elements are different.

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Atomic Theory Statement 3

Atoms cannot be subdivided, created, or destroyed in chemical reactions.

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Atomic Theory Statement 4

Atoms of different elements combine in simple whole-number ratios to form chemical compounds.

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Atomic Theory Statement 5

In chemical reactions, atoms are combined, separated, or rearranged.

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Electron charge

Electrons have a negative charge.

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Proton charge

Protons have a positive charge.

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Neutron charge

Neutrons have no charge.

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Electron mass

Electrons have very little mass.

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Proton mass

Protons have a significant mass.

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Neutron mass

Neutrons have a similar mass to protons.

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Atomic radius unit

Picometer (pm) is used to measure atomic radius.

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Electron Cloud

The region where electrons are found around the nucleus.

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Atomic Radius

Distance from the center of the nucleus to the outermost electron.

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Isotopes

Atoms of the same element with different numbers of neutrons, resulting in different mass numbers.

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Nuclear Symbol

A shorthand notation for an isotope, representing the element's symbol, atomic number, and mass number.

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Hyphen Notation

Another way to represent an isotope, using the element's name followed by its mass number with a hyphen.

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Protons

Positively charged particles found in the nucleus of an atom. Their number determines the element's identity.

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Neutrons

Neutral particles found in the nucleus of an atom. Their number influences the atom's mass but not its identity.

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Average Atomic Mass

The weighted average of the atomic masses of an element's naturally occurring isotopes.

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Weighted Average

An average calculated by considering the relative abundance of each item.

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Atomic Mass

The mass of an atom, usually measured in atomic mass units (amu).

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Natural Abundance

The percentage of an isotope present in a sample of the element as it occurs in nature.

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Atomic Number

The number of protons in the nucleus of an atom, which defines the element.

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Calculating Weighted Average

Multiply the mass of each isotope by its natural abundance (as a decimal fraction), and sum the products.

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Mixture of Isotopes

Elements frequently consist of atoms of different masses (isotopes), each with a specific natural abundance.

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Marble Analogy

The weighted average calculation for a mixture of elements can be visualized by a mixture of marbles of different weights

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Statistical Calculation

Average atomic mass is dependent on the relative proportions of isotopes naturally arising.

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Relative Abundance

The proportion of a particular isotope of an element relative to other isotopes of that element in a naturally occurring sample.

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Atomic mass unit (amu)

A unit of mass used to express atomic and molecular weights, equal to one-twelfth the mass of one carbon-12 atom.

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Copper-63

An isotope of copper with 29 protons and 34 neutrons.

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Copper-65

An isotope of copper with 29 protons and 36 neutrons.

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Calculating Average Atomic Mass

Multiplying the atomic mass of each isotope by its fractional abundance, then summing the products.

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Percentage Abundance

The percentage of a specific isotope relative to all isotopes of an element in a sample.

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Hydrogen-1

The most common isotope of Hydrogen, having 1 proton and 0 neutrons.

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Study Notes

Chapter 3: Atoms: The Building Blocks of Matter

  • Atoms are the fundamental building blocks of matter
  • Matter cannot be created or destroyed, only rearranged during chemical reactions and physical changes
  • Early philosophers debated whether materials had fundamental, indivisible particles (atoms)
  • Aristotle & Democritus: competing views on matter's composition.
  • 18th and 19th centuries scientists developed laws to explain how matter reacts and combines
  • The law of conservation of mass: mass is neither created nor destroyed during chemical reactions or physical changes
  • The law of definite proportions: a chemical compound always contains the same proportions (by mass) of its elements regardless of sample size or source
  • The law of multiple proportions: if two or more different compounds are composed of the same two elements, the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers
  • Dalton's atomic theory: explanation of the above laws; matter consists of atoms.
  • Atoms are indivisible, atoms of the same element are identical in mass, atoms of different elements differ in mass and properties, and atoms combine in small whole number ratios to form compounds.
  • Atoms are composed of smaller particles: electrons, protons, and neutrons
  • The atom is mostly empty space.
  • Experiments revealed negatively charged particles: electrons
  • Atoms have a dense, positively charged core: the atomic nucleus
  • Nucleus consists of protons and neutrons
  • Electrons orbit the nucleus in a large region surrounding the nucleus
  • Atomic radii are expressed in picometers (pm)
  • Atomic mass is a relative measure, expressed in unified atomic mass units (u) based on carbon-12
  • The periodic table organizes elements with increasing atomic number, which corresponds to the number of protons in each atom
  • Isotopes are atoms of the same element having different numbers of neutrons
  • Isotopes of an element have the same number of protons and electrons, but differing numbers of neutrons
  • Mass number: the sum of protons and neutrons in an atom
  • Average atomic mass: weighted average of the atomic masses of the naturally occurring isotopes of an element
  • The mole is a unit of measurement for the amount of substance
  • Avogadro's number is the number of particles in one mole of a substance (6.022 × 10^23 particles/mole)
  • Molar mass: the mass in grams of one mole of a substance

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Atoms: The Building Blocks of Matter - Chapter 3 PDF

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Explore the fundamental concepts of atoms, the building blocks of matter, in this quiz based on Chapter 3. Delve into the historical perspectives of Aristotle and Democritus, and understand key laws such as the conservation of mass and definite proportions. Test your knowledge on how matter interacts through various chemical reactions.

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