Atomic Structure and Periodic Table

Study Notes

An atom consists of:
- Protons (positively charged) in the nucleus
- Neutrons (no charge) in the nucleus
- Electrons (negatively charged) in energy levels around the nucleus
Atomic number: number of protons in an atom (defines the element)
Mass number: number of protons and neutrons in an atom (defines the isotope)
Atomic mass: average mass of an element's naturally occurring isotopes

Organizes elements by their atomic number and chemical properties
Elements are arranged in:
- Periods (rows): elements with similar energy levels
- Groups (columns): elements with similar chemical properties
Periodic trends:
- Atomic radius: decreases from left to right and increases down a group
- Electronegativity: increases from left to right and decreases down a group

A process involving the transformation of one or more substances
Types of chemical reactions:
- Synthesis: two or more substances combine to form a new substance
- Decomposition: a single substance breaks down into two or more substances
- Single displacement: one element replaces another in a compound
- Combustion: a substance reacts with oxygen to produce heat and light
Chemical equations: a representation of a chemical reaction using chemical formulas and arrows

The attractive forces between atoms that hold them together
Types of chemical bonds:
- Ionic bond: transfer of electrons between atoms (e.g., NaCl)
- Covalent bond: sharing of electrons between atoms (e.g., H2)
- Polar covalent bond: unequal sharing of electrons between atoms (e.g., HCl)
Bonding theories:
- Valence shell electron pair repulsion (VSEPR) theory: predicts molecular shape
- Molecular orbital (MO) theory: predicts molecular structure and bonding

An atom consists of protons, neutrons, and electrons, with protons and neutrons in the nucleus and electrons in energy levels around the nucleus.
The atomic number, which defines the element, is the number of protons in an atom.
The mass number, which defines the isotope, is the sum of protons and neutrons in an atom.
Atomic mass is the average mass of an element's naturally occurring isotopes.

The periodic table organizes elements by their atomic number and chemical properties.
Elements are arranged in periods (rows) and groups (columns), with similar energy levels in periods and similar chemical properties in groups.
Atomic radius decreases from left to right and increases down a group, while electronegativity increases from left to right and decreases down a group.

Electron configuration is the arrangement of electrons in an atom's energy levels, with each energy level (shell) having a specific capacity.
Subshells, including s, p, d, and f, also have specific capacities.
The Aufbau principle states that electrons occupy the lowest available energy level, while Hund's rule states that electrons occupy degenerate orbitals with parallel spin.
Electron configuration notation is written in the format 1s2 2s2 2p6, etc.

Chemical reactions involve the transformation of one or more substances, with types including synthesis, decomposition, single displacement, and combustion reactions.
Chemical equations represent chemical reactions using chemical formulas and arrows.

Chemical bonds are the attractive forces between atoms that hold them together, with types including ionic, covalent, and polar covalent bonds.
Ionic bonds involve the transfer of electrons between atoms, while covalent bonds involve the sharing of electrons.
Polar covalent bonds involve the unequal sharing of electrons between atoms.
Bonding theories, including VSEPR and MO theories, predict molecular shape and structure.