Chemistry Basics: Understanding Matter

Study Notes

An atom is the smallest unit of matter preserving original properties.
Atomic structure includes:
- 1st shell: holds 2 electrons
- 2nd shell: holds up to 8 electrons
- 3rd shell: can hold up to 18 electrons, usually stable at 8 electrons
An element is a substance that cannot be chemically broken down into simpler substances.
Elements are defined by their atomic number, which indicates the number of protons.
The periodic table organizes elements by chemical symbols, typically derived from their names (e.g., H for Hydrogen).

Isotopes have identical atomic numbers but different mass numbers.
Some isotopes are highly energetic and unstable, emitting radiation, utilized in nuclear medicine.
Applications of isotopes include:
- Cancer radiation therapy
- Radiotracers
- Treatment of thyroid disorders

A mixture consists of atoms from two or more elements physically intermixed.
Components of a solution:
- Solute: the substance that dissolves
- Solvent: the medium in which the solute dissolves (water is the primary solvent in the human body)
Concentration indicates the amount of solute in a solution (e.g., 10 grams of salt in 90 milliliters of water = 10% salt solution).
Solutions are mixtures formed without chemical changes, allowing for physical separation.

Valence electrons determine how atoms bond with others.
Example of ionic bonding: Sodium (Na) transfers its outer electron to Chlorine (Cl), resulting in charged particles known as ions.
Sodium has 11 protons and upon losing one electron, becomes a positively charged ion with a +1 charge.