Atoms

Atoms

Basic Atom Structure

• An atom is the smallest constituent unit of ordinary matter.
• Each atom is composed of protons, neutrons, and electrons.
• Protons and neutrons make up an atom’s nucleus.
• Electrons orbit around the nucleus in a cloud-like formation.
• The atomic number of an atom is the number of protons in its nucleus.
• The mass number of an atom is the total number of protons and neutrons in its nucleus.

Atomic Charge

• Protons carry a positive charge, electrons carry a negative charge, and neutrons are neutral.
• In a neutral atom, the number of protons and electrons are equal, balancing out the charge.
• Ions are atoms where the number of protons and electrons are not equal, resulting in a net charge.

Elements and Isotopes

• Elements are defined by the number of protons they contain, eg. all atoms of Oxygen have 8 protons.
• Isotopes are atoms of the same element (same number of protons) but with different numbers of neutrons, resulting in different atomic masses.
• Examples of isotopes are Carbon-12, which has 6 neutrons and Carbon-14, which has 8 neutrons. Both are isotopes of carbon.

Structure of an Electron

• Electrons occupy energy levels also known as shells.
• The first shell can hold up to 2 electrons, and the subsequent shells can hold up to 8 electrons.
• Electrons will always fill up the lower energy levels first before moving to the higher energy levels.

Bohr Model of an Atom

• The Bohr model is a simple way of visualising an atom’s structure.
• In this model, the nucleus is at the centre, and the electrons circle around it in fixed orbits, or energy levels.
• Each energy level can hold a specific number of electrons: 2 in the first level, 8 in the second, and 8 in the third.
• If an atom has more than 18 electrons, additional ones will populate the fourth energy level, which can hold up to 18 electrons.