General Chemistry 1: Foundations, Atomic Structure, and the Periodic Table

Introduction to Chemistry

What is Chemistry?

Chemistry is the study of the composition, structure, properties, and reactions of matter. It explores how substances interact, combine, and change to form new substances.

• Substances with the same composition and properties can have different functions. Example: Toothpaste brands may have similar chemical compositions but serve different purposes.

• Key Focus: Understanding matter at the molecular and atomic levels.

Tips for Success in Chemistry

• Engage with the material actively.

• Use available resources and practice regularly.

• Reach out for help when needed.

Mathematical Foundations in Chemistry

Quick Refresher: Slope

The slope of a line is a measure of its steepness, calculated as the ratio of the vertical change (rise) to the horizontal change (run).

• Formula: $\text{Slope} = \frac{\text{rise}}{\text{run}}$

• Example: If rise = 9.2 and run = 13, then $\text{Slope} = \frac{9.2}{13} = 0.71$

Equation of a Line

The equation of a straight line is typically written as:

• $y = mx + b$

• Where m is the slope and b is the y-intercept.

• Example: $y = (0.04)(x) + 22.3$

Positive and Negative Numbers

• Positive numbers are greater than zero; negative numbers are less than zero.

• Negative exponents in scientific notation indicate very small numbers.

Percentage Calculations

Percentages are used to express ratios as parts per hundred.

• Formula: $\text{Percentage} = \frac{\text{Part}}{\text{Total}} \times 100$

• Example: $\frac{11.6}{11.7} \times 100 = 99.1\%$

Scientific Notation

Scientific notation is used to express very large or very small numbers in the form:

• $a \times 10^n$ where a is the coefficient and n is the exponent.

• Example: $5.6 \times 10^4$, $3.2 \times 10^{-7}$

• Negative exponents indicate very small values.

Atoms and Elements

The Periodic Table

The periodic table organizes all known elements by increasing atomic number and similar properties.

• Groups: Vertical columns (1-18) with similar properties.

• Periods: Horizontal rows (1-7).

• Representative Elements: Groups 1A-8A (1, 2, 13-18).

• Transition Elements: Groups 3-12.

Group	Name	Examples
1A	Alkali Metals (very reactive)	Li, Na, K, Rb, Cs
2A	Alkaline Earth Metals	Be, Mg, Ca, Sr, Ba, Ra
7A	Halogens	F, Cl, Br, I, At
8A	Noble Gases	He, Ne, Ar, Kr, Xe, Rn, Og

Metals, Nonmetals, and Metalloids

• Metals: Shiny, ductile, conduct heat and electricity, usually solids (except Hg).

• Nonmetals: Dull, brittle, poor conductors, good insulators, low density and melting points.

• Metalloids: Have properties intermediate between metals and nonmetals.

Atomic Theory and Structure

Dalton's Atomic Theory

• All matter is made of tiny particles called atoms.

• Atoms of an element are identical and different from those of other elements.

• Atoms combine in simple ratios to form compounds.

Discovery of the Electron: Cathode Ray Experiment

• J.J. Thomson (1897) discovered that atoms contain negatively charged particles called electrons.

• This disproved the "plum pudding" model of the atom.

Electromagnetic Radiation

• Consists of energy particles that move as waves and particles (photons).

• Wavelength (λ): Distance between peaks of waves.

• Inverse Relationship: High energy = short wavelength; low energy = long wavelength.

Subatomic Particles

• Protons: Positive charge (+1), located in the nucleus.

• Neutrons: No charge (0), located in the nucleus.

• Electrons: Negative charge (-1), occupy space around the nucleus.

Atomic Number and Mass Number

• Atomic Number (Z): Number of protons in the nucleus; defines the element.

• Mass Number (A): Total number of protons and neutrons.

• Symbol Notation: $\ce{^{A}_{Z}X}$, where X is the element symbol.

• Electrons are not included in the mass number because their mass is negligible.

Isotopes

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

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

Ions

• Atoms are neutral when the number of protons equals the number of electrons.

• Cation: Positively charged ion (more protons than electrons).

• Anion: Negatively charged ion (more electrons than protons).

Additional info:

• Some context and terminology were inferred and expanded for clarity and completeness.

• Tables and diagrams referenced in the notes were recreated in text and HTML table format.