Atomic Structure and Subatomic Particles

Atomic Structure

• Atoms are the fundamental building blocks of matter.
• They are extremely small, far smaller than any microscope can see.
• A common item like a 50p coin contains a colossal number of atoms.

Atomic Dimensions

• Atomic radius: approximately 0.1 nanometers (1 x 10⁻¹⁰ m).
• A nanometer (nm) is one billionth of a meter.
• Nuclei are far smaller, with a radius around 1 x 10⁻¹⁵ m.

Subatomic Particles

• Atoms have three main subatomic parts: protons, neutrons, and electrons.

Nucleus

• Located at the atom's center.
• Contains protons and neutrons.
• The nucleus carries a positive charge due to protons.
• Almost all the atom's mass resides in the nucleus.

Electrons

• Electrons orbit the nucleus in specific shells.
• They are negatively charged.
• Electron shells determine the size of the atom.
• Electrons have negligible mass relative to protons and neutrons.

Charge Neutrality

• Atoms are electrically neutral, meaning the positive and negative charges balance each other out.
• This balance comes from an equal number of protons and electrons.

Ions

• Ions are electrically charged particles. This happens when the number of protons and electrons isn't equal.
• Example: A 2- ion has two more electrons than protons.

Atomic Number and Mass Number

• Atomic number = number of protons in an atom.
• Mass number = total number of protons and neutrons in an atom.
• Number of neutrons = mass number - atomic number.