Notes, summaries, assignments, exams, and problems for Chemistry

Atomic Structure and Electron Configuration

• Atomic number = number of protons
• Mass number = protons + neutrons
• Isotopes differ by the number of neutrons

Quantum Mechanics and Orbital Rules

• Orbitals: s (1 orbital), p (3), d (5), f (7)
• Aufbau Principle: Electrons fill the lowest energy orbitals first.
• Hund’s Rule: Electrons spread out before pairing up in orbitals.
• Pauli Exclusion Principle: No two electrons can have the same set of quantum numbers.

Photoelectron Spectroscopy (PES) Basics

• X-axis: Binding energy (values increase to the left).
• Peak height: Corresponds to the number of electrons.
• Position: Peaks farther to the left are closer to the nucleus.

Chemical

Part I: Temperature and Thermometers

Basic Concepts and Scales

1. Name the Three Scales of Temperature.

Ans: The three scales of temperature are:

• Celsius
• Fahrenheit
• Kelvin

2. How Are Temperature and Hotness Related?

Ans: Temperature and hotness of a body are directly related. The hotter a substance is, the higher its temperature.

3. Reading a Laboratory Thermometer: Eye Level Precaution

Ans: While reading the temperature on a laboratory thermometer, the eye must be at the level of the mercury in the stem to avoid parallax error and ensure an accurate reading.

4. How Does a Digital Thermometer Measure Temperature?

Ans: A digital thermometer does not use mercury. It utilizes internal heat sensors (such as a thermistor or thermocouple) to measure the temperature... Continue reading "Essential Science Q&A: Temperature, Thermometers, and Space Facts" »

Atomic Structure

• Protons — positive charge, found in nucleus
• Neutrons — no charge, found in nucleus
• Electrons — negative charge, orbit nucleus in energy levels

Key Terms

• Atomic Number (Z): number of protons
• Mass Number (A): protons + neutrons
• Isotopes: atoms of the same element with different numbers of neutrons
• Ions: atoms that gain or lose electrons
  • Gain electrons → negative ion (anion)
  • Lose electrons → positive ion (cation)

Important Formulas

• Mass Number: A = Z + N
• Average Atomic Mass: weighted average of all isotopes

Electron Configuration

Electrons fill energy levels from lowest to highest energy. Example: Oxygen (8 electrons) → 1s² 2s² 2p⁴

Types of Elements & Periodic Trends

Types of Elements

• Metals: shiny, conduct heat/electricity,

1. What Is Static Electricity?

Static electricity is the imbalance of electric charge accumulated on an object’s surface.

It is commonly observed in daily life, resulting in phenomena such as:

• Hair rising
• A balloon sticking to a wall

2. Atomic Structure and Electric Charge

Electric charge is determined by the components of the atom:

• Proton: Positive (+) charge (located in the nucleus)
• Neutron: Neutral (0) charge (located in the nucleus)
• Electron: Negative (–) charge (orbits the nucleus)

Charge states are defined by the balance of protons and electrons:

• Neutral Atom: Equal number of protons and electrons
• Positive Charge: More protons than electrons (net loss of electrons)
• Negative Charge: More electrons than protons (net gain of electrons)

3. Methods

Transition Metal Valency and Electron Orbitals

In transition metals, the energy gap between the 4s orbital (outer shell) and the 3d orbital (inner shell) is extremely small. Because they are so close in energy, it does not take much additional energy to remove electrons from the 3d subshell after the 4s electrons have already been lost.

Electron Loss and Oxidation States

• First electrons lost: The two electrons in the 4s orbital are typically lost first, which is why almost all transition metals have a common valency of +2.
• Subsequent electrons lost: Because the 3d electrons are nearby in energy, one or more of them can also be involved in bonding, leading to higher valencies like +3, +4, or even +7 (in the case of manganese).

Moreover, the presence... Continue reading "Transition Metal Chemistry and Energy Source Analysis" »

Vernier Caliper

A Vernier caliper is an instrument for making very accurate linear measurements introduced in 1631 by Pierre Vernier of France. It uses two graduated scales: a main scale similar to that on a ruler and an auxiliary scale, the vernier, which slides parallel to the main scale and enables readings to be made to a fraction of a division on the main scale. Vernier calipers are widely used in scientific laboratories and in manufacturing for quality-control measurements.

Five Rules for Determining Significant Figures

1. Non-zero digits are significant. For example, in 6575 cm there are four significant figures; in 0.543 there are three significant figures.
2. Leading zeros are not significant. Zeros that precede the first non-zero digit indicate

Essential Chemistry Formulas and Reference

Miscellaneous Formulas

• Area of a Circle: 3.14r²
• Volume: Area × Height
• Density: Mass / Volume
• % Composition of Element: [(# of atoms of element) × (atomic weight of element)] / formula weight of substance × 100
• Molarity: (moles of solute) / (volume of solution in Liters)
• Bond Order: (# shared electrons) - (# nonbonding electrons) / 2
• Pressure: Force / Area
• Pressure × Volume: nRT
• Density of Gas: (Pressure × Molar Mass) / (R × Temperature)
• Molarity of Gas: (Density × R × Temperature) / Pressure

Temperature and Chemical Conversions

• Celsius to Kelvin: K = C + 273.15
• Kelvin to Celsius: C = K - 273.15
• Celsius to Fahrenheit: F = 9/5(C) + 32
• Fahrenheit to Celsius: C = 5/9(F - 32)
• 1 amu: 1.66054 × 10⁻²⁴ g
• Grams

🥪 Chemistry and Physics Fundamentals

Key Formulas

Density Triangle:

• Density (D) = Mass (m) ÷ Volume (V)

• Mass (m) = Density (D) × Volume (V)

• Volume (V) = Mass (m) ÷ Density (D)

Other Core Formulas & Rules:

• Neutrons = Mass Number − Atomic Number

• Valence Electrons = Outermost shell electrons

• Charge = Protons − Electrons (for ions)

• Stable Octet = 8 valence electrons (or 2 for small atoms like Helium)

Chemical Bonding

• Ionic Bond = Metal + Non-metal (electrons are transferred)

• Covalent Bond = Non-metal + Non-metal (electrons are shared)

• Diatomic molecules: H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂

Power Formula:                   Energy Formula:
P = V × I                                E = P × t  

Concepts

• Conductors let

Catalytic Reforming Process Fundamentals

• Converts low-octane naphtha into high-octane reformate, which is used for gasoline blending and aromatics production.
• Feed is mixed with hydrogen, heated, and passed over a catalyst in fixed-bed reactors.
• Major reactions include dehydrogenation to aromatics, isomerization to branched paraffins, and mild hydrocracking.
• Operating conditions are typically 450–520 °C temperature and 10–45 atm pressure.
• The catalyst used is platinum on alumina or bimetallic Pt–Re on alumina.
• Main products are reformate, hydrogen, LPG, and light hydrocarbons.

Fluid Catalytic Cracking (FCC) Technology

1. FCC converts heavy gas oils into valuable products like high-octane gasoline, LPG, and olefins.
2. Preheated feed contacts hot,

Hybridization in Hydrocarbons

Ethane (C₂H₆)

Ethane is sp³ hybridized with a tetrahedral geometry and a bond angle of 109.5°. One sp³ orbital of each carbon atom undergoes internuclear axial overlapping to form a sigma (σ) bond. Three sp³ orbitals of each carbon atom undergo internuclear axial overlapping with the 1s orbital of hydrogen atoms to form three sigma bonds each.

Ethene (C₂H₄)

In C₂H₄, each carbon atom is sp² hybridized and lies in a trigonal planar geometry with a bond angle of 120°. Out of three sp² hybrid orbitals:

• One sp² orbital of one carbon atom undergoes internuclear axial overlapping with the sp² orbital of another carbon atom to form one sigma (σ) bond.
• Two sp² orbitals of each carbon atom undergo internuclear