Book Chapter 2 Notes: The Structure of Matter and the Chemical Elements

2 The Structure of Matter and the Chemical Elements

• Andre Gide Quote: "One doesn’t discover new lands without consenting to lose sight of the shore for a very long time."

• Chapter Overview: This chapter introduces the language of chemistry and the chemist's view of matter.

• Analogy to Learning to Drive: Chemistry, like driving, requires learning a new language and skills.

2.1 Solids, Liquids, and Gases

• Understanding Matter: Understanding the behavior of matter requires understanding its internal structure.

• Model of Matter: A simplified approximation of reality used for visualizing, explaining, and predicting physical phenomena.

• Basic Model of Matter:

  • All matter is composed of tiny particles (spheres).

  • These particles are in constant motion.

  • The amount of motion is related to temperature (increased temperature means increased motion).

  • Solids, gases, and liquids differ in the freedom of motion of their particles and the strength of attraction between them.

Solids

• Particle Arrangement: Spheres held closely together by strong mutual attractions.

• Particle Motion: Particles jostle in place due to being crowded and strongly attracted to each other.

• Effect of Heating: Increased temperature leads to faster-moving particles, causing them to collide more violently, pushing neighbors farther away, and resulting in expansion (Figure 2.1).

Liquids

• Transition from Solid: Heating a solid enough causes particles to move powerfully enough to displace surrounding particles, collapsing the organized structure and forming a liquid.

• Particle Arrangement: Particles are close together, but with more empty space than in solids.

• Volume: Constant at a constant temperature due to attractions between particles.

• Particle Movement: Particles move faster, attractions break and reform easily, allowing particles to change location freely and liquids to flow, taking on the shape of their container (Figure 2.2).

Gases

• Vaporization/Evaporation: Conversion of liquid to gas (Figure 2.3).

• Temperature Effect: Higher temperature leads to faster-moving particles, making them more likely to escape from the liquid.

• Particle Spacing: Particles are much farther apart than in solids or liquids.

• Volume Occupancy: Gas particles take up about 0.1% of the total volume, with the other 99.9% being empty space. In contrast, liquid particles fill about 70% of the total volume.

• Particle Movement: Each particle moves freely in a straight-line path until colliding with another particle or the container walls.

• Particle Interaction: Particles move fast enough to break any potential attractions, bouncing off each other after collisions.

• Volume and Shape: Gases expand to fill any shape or volume of the container due to rapid, ever-changing, and unrestricted movement of particles.

2.2 The Chemical Elements

• Dismantling Matter: Chemists dismantle matter to understand its components.

• Analyzing Salt Water: Salt water can be separated into simpler components (salt and water) through heating (distillation).

• Breaking Down Water: Water can be broken down into hydrogen and oxygen gases through electric current.

• Breaking Down Salt: Salt can be broken down into sodium metal and chlorine gas through electric current.

• Elements: Substances that cannot be chemically converted into simpler ones (hydrogen, oxygen, sodium, chlorine).

• Chemical Compounds: Water (hydrogen and oxygen) and salt (sodium and chlorine) are examples.

• Mixtures and Solutions: The mixture of salt and water.

• Number of Elements: By 2014, 118 elements had been discovered, but only some are found naturally on Earth.

• Unstable Elements: Some elements are unstable and undergo radioactive decay.

• Stable Elements: Of the 83 stable elements found in nature, only some are commonly used.

• Element Names and Symbols: Each element has a name and a symbol.

  • Some elements named after places (francium, californium).

  • Some named after scientists (meitnerium after Lise Meitner).

  • Some named for their source (hydrogen from “water forming”).

  • Some named for appearance (iodine from “violet”).

• Symbols:

  • First letter of the name (C for carbon).

  • First letter and a later letter (Cl for chlorine, Co for cobalt).

  • From Latin names (Na for sodium from natrium, Au for gold from aurum).

  • Temporary names and three-letter symbols for recently discovered elements.
    *Table 2.1 Common Elements
    Aluminum (Al), Gold (Au), Oxygen (O)
    Argon (Ar), Helium (He), Phosphorus (P)
    Barium (Ba), Hydrogen (H), Platinum (Pt)
    Beryllium (Be), Iodine (I), Potassium (K)
    Boron (B), Iron (Fe), Silicon (Si)
    Bromine (Br), Lead (Pb), Silver (Ag)
    Cadmium (Cd), Lithium (Li), Sodium (Na)
    Calcium (Ca), Magnesium (Mg), Strontium (Sr)
    Carbon (C), Manganese (Mn), Sulfur (S)
    Chlorine (Cl), Mercury (Hg), Tin (Sn)
    Chromium (Cr), Neon (Ne), Uranium (U)
    Copper (Cu), Nickel (Ni), Xenon (Xe)
    Fluorine (F), Nitrogen (N), Zinc (Zn)

2.3 The Periodic Table of the Elements

• Periodic Table: A basic tool that organizes elements to reveal their properties.

• Organization: Elements are organized so that those in the same vertical column have similar characteristics.

• Groups/Families: Vertical columns are called groups or families, numbered 1-18, with some having specific names (e.g., Group 18: Noble Gases).

• Numbering Conventions: Two common systems exist for numbering columns (1-18 and A/B groups), also Roman numerals with the A- and B-group convention.

• Metal Characteristics: Shiny metallic luster, good conductors of heat and electricity, malleable.

• Nonmetal Characteristics: Varying states (gas, solid, liquid), colors, and textures; do not possess metal characteristics.

• Metalloids/Semimetals: Elements with some, but not all, metal characteristics.

• Blocks of Elements:

  • Representative/Main-Group Elements: Groups 1, 2, and 13-18 (A groups).

  • Transition Metals: Groups 3-12 (B groups).

  • Inner Transition Metals: 28 elements at the bottom of the table.

• Periods: Horizontal rows on the periodic table (seven periods in total).

• Room Temperature States: Most elements are solid, two are liquid (Hg and Br), and eleven are gas (H, N, O, F, Cl, and noble gases).

Exercise 2.1 - Elements and the Periodic Table

Exercise 2.2 - Group Names and the Periodic Table

helium: Noble Gases
chlorine: Halogens
magnesium: Alkaline Earth Metals
sodium: Alkali Metals

2.4 The Structure of the Elements

• Element Differences: Explained by internal structure, specifically atoms.

• Atom: The smallest part of an element that retains its chemical characteristics.

• Atom Size: Approximately 10^{-10} meters in diameter.

• Atom Composition: Protons, neutrons, and electrons.

• Protons: Positive charge.

• Neutrons: No charge.

• Electrons: Negative charge.

• Particle Mass: Neutrons are the most massive, followed by protons, then electrons (about 2000 times less massive than protons/neutrons).

• Atomic Mass Unit (amu or u): 1/12 the mass of a carbon atom with 6 protons, 6 neutrons, and 6 electrons.

• Charge:

  • Opposite charges attract.

  • Like charges repel.

  • Electron charge is -1, proton charge is +1.

• Nucleus: The core of the atom consisting of protons and neutrons.

• Nucleus Size: Approximately 10^{-15} meters in diameter (1/100,000 the diameter of the atom).

• Electron Cloud: Electrons visualized as generating a cloud of negative charge surrounding the nucleus (Figure 2.8).

• Ions: Charged particles formed when atoms lose or gain electrons.

• Cations: Positively charged ions formed when atoms lose electrons (e.g., Na^{+}).

• Anions: Negatively charged ions formed when atoms gain electrons (e.g., Cl^{-}).

Example 2.1 - Cations and Anions

a: Anion, -3
b: Cation, +1

Exercise 2.3 - Cations and Anions

a: Cation, +2
b: Anion, -1

• Isotopes: Atoms of the same element with the same number of protons but different numbers of neutrons (e.g., hydrogen isotopes).

• Atomic Number: The number of protons in an atom (also the number of electrons in an uncharged atom).

• Mass Number: The sum of protons and neutrons in an atom's nucleus.

• Isotope Notation: Element symbol followed by mass number (e.g., H-1).
  *Number of Protons + Number of Neutrons = Mass Number
  13 + 14 = 27

2.5 Common Elements

• Gas, Liquid, and Solid Elements: Described based on particle nature.

• Noble Gases: Single atoms moving independently in straight-line paths (Figure 2.12).

• Hydrogen Gas: Diatomic molecules (H2) formed by covalent bonds (sharing of two electrons) between two hydrogen atoms (Figures 2.13, 2.14, 2.15).

• Molecule: An uncharged collection of atoms held together with covalent bonds.

• Diatomic Elements: N2, O2, F2, Cl2, Br2, and I2

• Bromine (Liquid): Diatomic molecules in a liquid state (Figure 2.16).

• Iodine (Solid): Ordered arrangement of I_2 molecules (Figure 2.17).

• Metallic Elements: Atoms release electrons, forming cations, with electrons moving freely throughout the solid (sea of electrons model) (Figure 2.18).

• Metallic Properties: Freely moving electrons explain good conductivity of electric currents.

Atomic mass unit (u or amu) = 1/12 the mass of a carbon atom that has 6 protons, 6 neutrons, and 6 electrons.