Atomic Structure and Properties Quiz

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.