Foundational Topics in GOB Chemistry: Elements, Atomic Structure, and Measurement

Introduction to GOB Chemistry

This study guide outlines the foundational topics in General, Organic, and Biological (GOB) Chemistry, focusing on the structure of matter, chemical formulas, measurements, atomic structure, and laboratory techniques. These topics are essential for understanding the principles of chemistry as applied to health sciences and related fields.

The Elements and Their Symbols

Chemical Symbols

• Elements are pure substances consisting of only one type of atom, each represented by a unique chemical symbol (e.g., H for hydrogen, O for oxygen).

• Symbols are typically one or two letters, with the first letter capitalized.

Chemical Formulas

• Chemical formulas represent the types and numbers of atoms in a compound (e.g., H2O for water).

• Subscripts indicate the number of each atom present.

The Periodic Table

Groups and Periods

• Groups are vertical columns; elements in the same group have similar chemical properties.

• Periods are horizontal rows; properties change progressively across a period.

Classification of Elements

• Main group elements: Groups 1, 2, and 13-18.

• Transition metals: Groups 3-12.

• Inner transition elements: Lanthanides and actinides.

• Metals, non-metals, and metalloids: Classified by physical and chemical properties.

• Special groups:

  • Noble gases: Group 18, inert gases.

  • Halogens: Group 17, highly reactive non-metals.

  • Alkali metals: Group 1, very reactive metals.

  • Alkaline earth metals: Group 2, reactive metals.

Measurements in Chemistry

The Metric System

• Standard system for scientific measurements.

• Units: meter (m), liter (L), gram (g), second (s), etc.

• Prefixes: kilo- (k), centi- (c), milli- (m), etc.

Uncertainty and Significant Figures

• All measurements have some degree of uncertainty.

• Significant figures indicate the precision of a measurement.

• Use appropriate measuring devices and record all certain digits plus one estimated digit.

Percentages and Density

Percentages

• Used to express concentration or composition.

• Calculated as: $\text{Percent} = \frac{\text{Part}}{\text{Whole}} \times 100$

Density

• Density is the mass per unit volume of a substance.

• Formula: $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

• Units: g/mL or g/cm3

Atomic Structure

Subatomic Particles

• Protons: Positively charged, found in the nucleus.

• Neutrons: Neutral, found in the nucleus.

• Electrons: Negatively charged, found in the electron cloud.

Atomic Number and Mass

• Atomic number (Z): Number of protons in the nucleus.

• Atomic mass (A): Total number of protons and neutrons.

Isotopes

• Atoms of the same element with different numbers of neutrons.

• Isotopes have the same atomic number but different mass numbers.

Atomic Symbols

• Written as: $^{A}_{Z}\text{X}$, where X is the element symbol, A is the mass number, and Z is the atomic number.

Quantum Mechanical Model of the Atom

Energy Levels and Orbitals

• Electrons occupy specific energy levels (shells) around the nucleus.

• Orbitals are regions of space where electrons are likely to be found.

• Energy levels are designated by principal quantum numbers (n = 1, 2, 3, ...).

Electron Configurations

• Describes the arrangement of electrons in an atom.

• Follows the Aufbau principle, Pauli exclusion principle, and Hund's rule.

• Example: $1s^2 2s^2 2p^6$ for neon.

• Orbital diagrams use arrows to represent electron spins.

• Valence electrons are electrons in the outermost shell, important for chemical bonding.

Stability of Isotopes

• Stable isotopes do not undergo radioactive decay.

• Unstable isotopes (radioisotopes) decay by emitting radiation.

Radioactivity

Types of Emission

• Alpha (α) emission: Loss of a helium nucleus ($^4_2\text{He}$).

• Beta (β) emission: Conversion of a neutron to a proton with emission of an electron.

• Positron emission: Conversion of a proton to a neutron with emission of a positron.

• Gamma (γ) emission: Emission of high-energy photons.

Ions and Nomenclature

Formation of Ions

• Cations: Positively charged ions (loss of electrons).

• Anions: Negatively charged ions (gain of electrons).

• Monatomic ions: Single-atom ions (e.g., Na+, Cl-).

• Polyatomic ions: Ions composed of multiple atoms (e.g., SO42-).

Naming Compounds

• Use systematic rules for naming ionic and molecular compounds.

• Acids: Compounds that release H+ in water (e.g., HCl is hydrochloric acid).

• Bases: Compounds that release OH- in water (e.g., NaOH is sodium hydroxide).

Covalent Bonds and Lewis Structures

• Covalent bonds: Sharing of electron pairs between atoms.

• Some elements exist as diatomic molecules (e.g., H2, O2).

• Lewis structures represent bonding and lone pairs of electrons.

• Single, double, and triple bonds indicate the number of shared electron pairs.

Laboratory Measurements and Experiments

Types of Laboratory Glassware

• Beakers, graduated cylinders, pipettes, burettes, etc.

• Each type has specific uses and accuracy levels.

Measurement Techniques

• Volume by displacement: Used to measure irregular objects.

• Density calculations: Use mass and volume measurements.

• Conversions: Mass to volume and vice versa.

Experiment: Determination of Concentration/Spectrophotometry

• Color observed and transmitted relates to wavelength absorbed.

• Blanks and calibration are used to ensure accuracy in spectrophotometric measurements.

Summary Table: Classification of Elements

Category	Location on Periodic Table	Key Properties
Main group elements	Groups 1, 2, 13-18	Predictable valence electron configurations
Transition metals	Groups 3-12	Variable oxidation states, form colored compounds
Inner transition elements	Lanthanides and actinides	Radioactive, used in specialized applications
Metals	Left and center	Conductive, malleable, ductile
Non-metals	Upper right	Poor conductors, brittle (if solid)
Metalloids	Stair-step line	Properties intermediate between metals and non-metals