Atoms and Their Fundamental Particles
Atoms are the building blocks of all matter, including living things. They are incredibly small, beyond the reach of even powerful microscopes. Each atom is composed of three main types of particles: protons, neutrons, and electrons.
Definition: An atom is the smallest unit of matter that retains the properties of an element.
The Nucleus
The nucleus is the dense central core of an atom, containing protons and neutrons.
Highlight: The nucleus contains nearly all of the atom's mass and has a positive charge due to the presence of protons.
Protons
- Positively charged particles
- Located in the nucleus
- Have a relative mass of 1
Vocabulary: Protons are subatomic particles with a positive electric charge.
Neutrons
- Neutral particles (no charge)
- Located in the nucleus alongside protons
- Have a relative mass of 1
Example: The term "neutron" comes from "neutral," reflecting its lack of electric charge.
Electrons
- Negatively charged particles
- Orbit the nucleus in electron shells
- Have a negligible mass (relative mass of 0)
Highlight: Electrons are much smaller than protons and neutrons but occupy a large space around the nucleus.
Atomic Structure and Charge
In a neutral atom, the number of protons equals the number of electrons, resulting in an overall neutral charge.
Definition: The atomic number of an element is equal to the number of protons in its nucleus.
Calculating Particles
To determine the number of neutrons in an atom:
- Identify the mass number (total protons and neutrons)
- Subtract the atomic number (number of protons) from the mass number
Example: For sodium (Na) with mass number 23 and atomic number 11, the number of neutrons is 23 - 11 = 12.
Ions: Charged Atoms
Ions are atoms or groups of atoms that have gained or lost electrons, resulting in a net electric charge.
Definition: An ion is an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
Example: An ion with a charge of -2 has two more electrons than protons.