Intro to Chem!

Ichi's Digital Laboratory

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Chemistry Notes

Chemistry Notes

Chemistry is the study of matter, its properties, and its composition.

Quick Chemistry Facts!

• Atoms are the basic units of matter.
• Elements are made of one type of atom.
• Chemical reactions form new substances.

Pure Substances!

Matter - Anything that has mass and occupies space.

Pure Substance - Has a fixed composition; includes elements and compounds.

Element - Made of one type of atom; cannot be broken down.

Compound - Made of two or more elements chemically combined.

Mixture - Two or more substances physically combined; can be separated.

Atoms, Molecules, and Ions

• 1. Electronic Structure of atoms - how electrons are arranged in an atom's energy levels (or shells).
• 2. Pauli Exclusion Principle - Each orbital can hold 2 electrons with opposite spins
• 3. Hund's Rule - Electrons fill empty orbitals first before pairing up.
• Photo Source: Science Notes
• 4. Aufbau Principle - electrons fill the lowest energy first.
• Photo Source: BYJU's The Learning App

Chemical Bonding

Joining of atoms to form compounds or molecules. Atoms bond to become more stable, usually by completing their outer electron shells.

Types of Chemical Bonds:

• 1. Ionic Bond - metals + nonmetals = ionic compounds
• 2. Covalent Bond - nonmetals + nonmetals = molecular compounds
• 3. Metallic Bond - metals + metals =metallic substance

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Periodic Table

Periodic Table

The periodic table organizes elements according to their atomic number and properties.

Here are some of the most common elements!

• Hydrogen — H — Atomic Number: 1
• Helium — He — Atomic Number: 2
• Carbon — C — Atomic Number: 6
• Nitrogen — N — Atomic Number: 7
• Oxygen — O — Atomic Number: 8
• Sodium — Na — Atomic Number: 11
• Chlorine — Cl — Atomic Number: 17
• Iron — Fe — Atomic Number: 26

Here is the actual Periodic Table!

Photo Source: Fabio Crameri.

Periodicity

Periodicity is the repeating patterns in properties of elements across the periodic table

• 1. Atomic Radius (Size of Atom) - Across a period: more protons pull electrons closer (same shell → smaller). Down a group: more shells → atoms get bigger
• 2. Ionization Energy (energy to remove 1 electron) - More electrons in outer shell = harder to remove. Farther from nucleus = easier to remove
• 3. Electronegativity (pull on shared electrons) - More protons + almost full outer shell = stronger pull. Bigger atoms = weaker pull
• 4. Metallic Character - Elements on the left (like Na, K) do this better than the right (like Cl)

Photo Source: Mirek2 / Wikimedia Commons

Periodic Table Groups and Families

• Group 1: Alkali Metals - Very reactive, soft metals
• Group 2: Alkaline Earth Metals - Reactive, found in rocks
• Groups 3-12: Transition Metals - Hard, shiny, good conductors
• Group 13: Boron Group - Less Reactive, Mixed types, includes aluminum
• Group 14: Carbon Group - Forms many compounds
• Group 15: Nitrogen Group - Used in air and fertilizers
• Group 16: Oxygen Group - Needed for breathing, includes sulfur
• Group 17: Halogens - Very reactive, forms salts
• Group 18: Noble Gases - Stable, nonreactive gases

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