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

Introduction to Chemistry

What is Chemistry?

Chemistry is the scientific 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: All toothpaste brands have similar chemical compositions but serve different functions (e.g., whitening, sensitivity).

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

Tips for Success in Chemistry

• Engage with the material actively.

• Use available resources (textbooks, notes, study groups).

• Practice problem-solving regularly.

• Reach out for help when needed.

Mathematical Foundations in Chemistry

Understanding Slope

The slope of a line is a measure of how much the y-value changes for a given change in the x-value. It is essential for interpreting graphs and data in chemistry.

• Formula: $\text{Slope} = \frac{\text{Rise}}{\text{Run}}$

• Example: If y changes from 72.3 to 73.3 as x changes from 50 to 51, then $\text{Slope} = \frac{73.3 - 72.3}{51 - 50} = 1.0$

Equation of a Line

The equation of a straight line is fundamental for analyzing trends in chemical data.

• General Form: $y = mx + b$

• Where: m = slope, b = y-intercept

• Example: $y = (0.04)(x) + 72.3$

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 proportions in chemical calculations.

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

• Example: $\frac{11.6\,g}{11.6\,g + 0.4\,g} \times 100 = 96.7\%$

Scientific Notation

Scientific notation is used to express very large or very small numbers efficiently.

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

• Example: $3.2 \times 10^4$, $7.5 \times 10^{-7}$

• Negative exponent means the number is very small.

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 (B groups).

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

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: Properties intermediate between metals and nonmetals.

Atomic Theory and Structure

Dalton's Atomic Theory

John Dalton proposed that all matter is made of tiny particles called atoms. Atoms of each element are identical and different from those of other elements.

• Atoms combine in fixed ratios to form compounds.

• Atoms are rearranged in chemical reactions but not created or destroyed.

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

Electromagnetic radiation consists of energy particles that move as waves.

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

• High energy = short wavelength; Low energy = long wavelength.

Subatomic Particles

• Protons: Positive charge (+1)

• Neutrons: No charge (0)

• Electrons: Negative charge (–1)

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

• Cation: Atom with more protons than electrons (positive charge).

• Anion: Atom with more electrons than protons (negative charge).

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

Summary Table: Subatomic Particles

Particle	Symbol	Charge	Location
Proton	p+	+1	Nucleus
Neutron	n0	0	Nucleus
Electron	e–	–1	Outside nucleus

Additional info: These notes provide foundational concepts for General, Organic, and Biological (GOB) Chemistry, including atomic theory, periodic trends, and basic mathematical skills essential for success in college-level chemistry.