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Questions and Answers
What does atomic number, Z, represent for atoms of the same element?
What does atomic number, Z, represent for atoms of the same element?
How much heavier is an oxygen atom compared to a hydrogen atom?
How much heavier is an oxygen atom compared to a hydrogen atom?
Who developed the modern view of the atom?
Who developed the modern view of the atom?
Which statement about atoms is true?
Which statement about atoms is true?
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What can be inferred about the number of atoms in a teaspoon of water compared to the Atlantic Ocean?
What can be inferred about the number of atoms in a teaspoon of water compared to the Atlantic Ocean?
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Who discovered radioactivity, providing evidence of the atomic structure?
Who discovered radioactivity, providing evidence of the atomic structure?
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What is the charge of a neutron?
What is the charge of a neutron?
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Which particle in the atom has a significantly smaller mass compared to protons and neutrons?
Which particle in the atom has a significantly smaller mass compared to protons and neutrons?
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What constitutes the nucleus of an atom?
What constitutes the nucleus of an atom?
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In an atom, the number of electrons is equal to:
In an atom, the number of electrons is equal to:
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What best describes the composition of an atom?
What best describes the composition of an atom?
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Which of the following atoms has the largest mass?
Which of the following atoms has the largest mass?
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What phenomenon represents the spontaneous disintegration of elements?
What phenomenon represents the spontaneous disintegration of elements?
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What is Avogadro's number?
What is Avogadro's number?
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What is the molar mass of carbon-12 ($^{12}C$)?
What is the molar mass of carbon-12 ($^{12}C$)?
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Which of the following statements is true regarding the modern periodic table?
Which of the following statements is true regarding the modern periodic table?
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If you have 0.200 g of magnesium (Mg), what is knowledge required to find the number of atoms present?
If you have 0.200 g of magnesium (Mg), what is knowledge required to find the number of atoms present?
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What represents the concept of one mole in terms of carbon ($^{12}C$)?
What represents the concept of one mole in terms of carbon ($^{12}C$)?
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What is the standard element against which all others are measured?
What is the standard element against which all others are measured?
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Which of the following correctly represents the mass number (A) of a boron atom with 5 protons and 5 neutrons?
Which of the following correctly represents the mass number (A) of a boron atom with 5 protons and 5 neutrons?
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How many neutrons does Boron-11 have?
How many neutrons does Boron-11 have?
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What distinguishes isotopes of the same element?
What distinguishes isotopes of the same element?
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Which of the following is a radioactive isotope of hydrogen?
Which of the following is a radioactive isotope of hydrogen?
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What is the atomic representation of Boron-10?
What is the atomic representation of Boron-10?
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Which element is associated with the use of technetium-99 in medical scans?
Which element is associated with the use of technetium-99 in medical scans?
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When measuring a carbon atom's mass standard, what is the value assigned to it?
When measuring a carbon atom's mass standard, what is the value assigned to it?
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Which of the following elements is classified as an alkali metal?
Which of the following elements is classified as an alkali metal?
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Which of these groups contains elements that generally react with water?
Which of these groups contains elements that generally react with water?
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What is unique about gallium among the metals listed?
What is unique about gallium among the metals listed?
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Which of the following elements is NOT part of Group 2A?
Which of the following elements is NOT part of Group 2A?
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Why does aluminum resist corrosion?
Why does aluminum resist corrosion?
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In which category would you classify magnesium?
In which category would you classify magnesium?
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Which of these compounds includes aluminum as a component?
Which of these compounds includes aluminum as a component?
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What characteristic distinguishes transition metals from alkali and alkaline earth metals?
What characteristic distinguishes transition metals from alkali and alkaline earth metals?
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What is the composition of Ruby?
What is the composition of Ruby?
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Which of the following elements are part of Group 6A?
Which of the following elements are part of Group 6A?
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What is the first isolated form of phosphorus and from where was it derived?
What is the first isolated form of phosphorus and from where was it derived?
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Which of the following is NOT a noble gas?
Which of the following is NOT a noble gas?
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Which compound is represented by SiO2?
Which compound is represented by SiO2?
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What type of structure does elemental sulfur have?
What type of structure does elemental sulfur have?
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Which transition metal will produce iron(III) oxide when exposed to air?
Which transition metal will produce iron(III) oxide when exposed to air?
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Which of the following is a halogen?
Which of the following is a halogen?
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Study Notes
Chemistry and Chemical Reactivity
- This is a chemistry textbook, 6th edition, by John C. Kotz, Paul M. Treichel, and Gabriela C. Weaver.
- Chapter 2 focuses on atoms and elements.
- Lectures and information are from John Kotz.
Atoms and Elements
- Atoms are composed of a nucleus (protons and neutrons) and an electron cloud.
- Elements differ in the number of protons in their nucleus.
- Relative abundances of elements vary significantly.
- Hydrogen, Helium, Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine, Neon, Sodium, Magnesium, Aluminum, Silicon, Phosphorus, Sulfur, Chlorine, Argon, Potassium, Calcium, Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, and Zinc are elements shown in the relative abundance graph.
Radioactivity
- Marie Curie (1876-1934) discovered radioactivity.
- Radioactivity is the spontaneous disintegration of certain elements into smaller parts.
- This is one piece of evidence that atoms are made of smaller particles.
Types of Radioactive Emissions
- Alpha particles are positively charged and are attracted to negative plates.
- Beta particles are negatively charged and are attracted to positive plates.
- Gamma rays are neutral and are undeflected.
- Alpha particles have a low penetrating power.
- Beta particles have a moderate penetrating power.
- Gamma rays have a high penetrating power.
- Alpha particles can be stopped by paper.
- Beta particles can be stopped by a thin sheet of aluminum.
- Gamma rays can be stopped by several centimeters of lead or concrete.
Atomic Composition
- Protons: Positive electrical charge, mass of 1.672623 x 10⁻²⁴ g, relative mass of 1.007 atomic mass units (u).
- Electrons: Negative electrical charge, relative mass of 0.0005 u.
- Neutrons: No electrical charge, mass of 1.009 u.
- Atoms are mostly empty space, with protons and neutrons in the nucleus.
- The number of electrons equals the number of protons.
- Electrons are in a space around the nucleus.
- Atoms are extremely small.
Isotopes
- Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
- Boron-10 has five protons and five neutrons; Boron-11 has five protons and six neutrons.
- The different isotopes of an element have different masses.
- Atoms of the same element have the same atomic number.
- Atoms of the same element may have different mass numbers.
Atomic Weight
- Atomic weight tells the relative mass of one atom of an element compared to another element's atom.
- It's also the mass per 1000 atoms of one element relative to 1000 atoms of another element.
- The standard for atomic weight measurement is carbon.
Mass Number
- Mass number (A) = number of protons + number of neutrons.
- A boron atom can have 10 u (boron-10).
- Carbon-12 is the mass standard, with a mass of 12 atomic mass units (u).
Boron in Death Valley
- Death Valley is a source of borax and other boron-containing minerals.
- Borax has been transported out of Death Valley in wagons pulled by 20 mules.
Isotope Composition
- Isotope Composition data is presented in a table with missing information, including electrons, protons, and neutrons for sulfur-32 and bromine-79.
Isotopes & Their Uses
- Technetium-99 (⁹⁹₄₃Tc) emits gamma rays, used for heart scans.
Masses of Isotopes
- Isotope masses are determined by mass spectrometry.
- A mass spectrum is a plot of the relative abundance of charged particles versus the ratio of mass to charge (m/z).
Mass Spectrum of C₆H₅Br
- The mass spectrum plots the relative abundance of charged particles against mass-to-charge (m/e) ratios.
- Peaks in the spectrum correspond to different isotopes and their abundances in the molecule.
- 158: (¹²C)(¹H)₈₁Br; 156: (¹²C)₆(¹H)₅⁷⁹Br
Isotopes
- Because of the presence of isotopes, the mass of a collection of atoms has an average mass.
- Boron's average atomic weight is 10.8 u.
- Boron-10 is 19.9% abundant, and Boron-11 is 80.1% abundant.
Isotopes & Atomic Weight
- Different isotopes exist for the same element.
- The average mass of a sample is called the atomic weight.
Counting Atoms
- Chemistry needs a "counting unit" – The mole.
- One mole is the amount of a substance containing as many particles as there are in 12.0 g of ¹²C.
- This quantity is called Avogadro's number (6.02214199 x 10²³).
Molar Mass
- One mole of ¹²C = 12.00 g of ¹²C atoms, and 6.022 x 10²³ atoms of ¹²C.
- The molar mass of an element takes into account all its isotopes.
- Carbon's molar mass is 12.011 g/mol.
One-mole Amounts
- The mass of one mole of an element in grams is numerically equal to its atomic weight.
Periodic Table
- Dmitri Mendeleev developed the modern periodic table, arguing that element properties are periodic functions of their atomic weights.
- We now know that element properties are periodic functions of their atomic numbers.
Periods in the Periodic Table
- The periodic table is arranged in periods (rows) and groups (columns).
- Elements in the same group have similar properties.
- Elements in the same period follow a pattern in properties.
Groups/Families in the Periodic Table
- The vertical columns on the periodic table are called groups or families.
- Elements in the same group share similar chemical properties.
Regions of the Periodic Table
- The periodic table can be divided into regions based on the types of elements.
- Elements fall within regions of the table with the following properties: main group metals, transition metals, metalloids, and nonmetals.
Element Abundance
- The abundance of elements varies.
- The most abundant elements in the solar system are hydrogen, helium, oxygen, carbon, nitrogen, and silicon.
Hydrogen
- Shuttle engines use hydrogen fuel.
Group 1A: Alkali Metals
- Alkali metals react with water.
- Sodium metal can be cut.
- Potassium reacts violently with water
Group 2A: Alkaline Earth Metals
- Alkaline earth metals are reactive.
- Magnesium will quickly form magnesium oxide when exposed to air.
Group 3A: B, Al, Ga, In, TI
- Aluminum resists corrosion in nitric acid.
- Gallium is a liquid metal at room temperature.
Gems & Minerals
- Sapphires are aluminum oxide (Al₂O₃) with impurities (like iron or titanium) controlling color.
- Rubies are aluminum oxide (Al₂O₃) with chromium impurity.
Group 4A: C, Si, Ge, Sn, Pb
- Silicon dioxide (SiO₂) is quartz.
- Diamond is an allotrope of carbon
Group 5A: N, P, As, Sb, Bi
- White and red phosphorus are allotropes of phosphorus.
- Ammonia (NH₃) is a compound of nitrogen and hydrogen.
Phosphorus
- Phosphorus was first extracted from urine in 1669.
Group 6A: O, S, Se, Te, Po
- Sulfur (elemental S) forms ring structures.
Group 7A: Halogens
- Fluorine, Chlorine, Bromine, Iodine, Astatine are halogens.
Group 8A: Noble Gases
- Helium, Neon, Argon, Krypton, Xenon, Radon are noble gases.
Transition Elements
- Iron in air forms iron(III) oxide.
- Transition elements are located in the middle of the periodic table.
- Lanthanides and actinides are two rows at the bottom of the periodic table, considered to be transition metals.
Colors of Transition Metal Compounds
- Transition metal compounds exhibit varied colors due to their electronic properties.
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Description
Test your knowledge of atomic structure, including concepts such as atomic number, mass, and the nature of particles within an atom. This quiz covers foundational principles about atoms, discoveries in atomic theory, and the characteristics of elements on the periodic table.
