Atomic Structure and Subatomic Particles

Atomic Structure

• Atoms are composed of a minute, positively charged nucleus and negatively charged electrons.
• The mass of an atom is concentrated in its nucleus.
• The electron configuration can be deduced from the atomic number.
• Atoms are fundamental building blocks of everything.
• Atoms have been theorized about for over 2500 years.
• Experimental evidence for atoms emerged in the 19th century.
• Atoms are too small to be seen directly.
• All atoms of a given element have identical chemical properties.
• Atoms of different elements have different properties.
• Atoms consist of subatomic particles.
• Atoms are largely empty space.
• Atoms are made up of protons, neutrons, and electrons.

Subatomic Particles

• Protons have a positive charge.
• Neutrons have no charge.
• Electrons have a negative charge.
• Relative masses and charges are given in the IB data booklet.
• The mass of the electron is negligible compared to protons and neutrons.
• Protons and neutrons are collectively called nucleons.
• The nucleus is a small, dense, positively charged core.
• Electrons occupy the space outside the nucleus.
• Isotopes are atoms of the same element with varying neutron numbers.

Atomic Number and Mass Number

• Atomic number (Z) is the number of protons.
• Mass number (A) is the sum of protons and neutrons.
• Isotopes have the same atomic number (Z) but different mass numbers (A).

Atomic Number

• The atomic number identifies the element.
• The atomic number is equal to the number of protons.

Mass Number

• The mass number is the sum of protons and neutrons in an atom.

Isotopes

• Atoms of the same element with different mass numbers are called isotopes.
• These atoms have the same number of protons but different numbers of neutrons.
• Isotopes have different physical properties (e.g., boiling and melting points).

Nature of Science

• Scientific knowledge is continually evolving.
• New technologies facilitate scientific discoveries.
• Scientific ideas are often initially speculative before gaining experimental support.
• Scientists' work often involves collaborations and diverse perspectives.
• Models can be used to explain processes that may not be observable directly.
• Models are simplifications of reality, which may not be entirely accurate.
• Modifications and expansions to models happen as more data is collected.
• Models are adjusted or replaced when they are no longer aligned with observations.

Electron Configuration

• Electrons occupy specific energy levels (shells).
• Each energy level can hold a maximum number of electrons. (2n²).
• Each main energy level is divided into sub-levels (s, p, d, f).
• Sub-levels consist of orbitals.
• Each orbital can hold a maximum of two electrons with opposite spins.
• Hund’s rule describes the filling of orbitals within a sublevel.
• The Pauli exclusion principle indicates that each orbital can hold only two electrons.

Atoms Contain Electrons

• Electrons were discovered in the late 19th century.
• Different metals produce streams of negatively charged particles (electrons) when a high voltage is applied.
• Atoms contain electrons surrounding the nucleus.
• The electron configuration provides information about the arrangement of electrons within the atom.

Electromagnetic Spectrum

• Electromagnetic radiation is a form of energy that travels as waves.
• Different types of electromagnetic radiation have different wavelengths.
• The wavelength and frequency of radiation are related: c=νλ
• Electromagnetic spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
• Different regions of the electromagnetic spectrum correspond to different energies.
• Emission spectra are produced when excited electrons return to lower energy levels, giving off specific wavelengths of light..
• Atoms have unique emission spectra that can be used for identification

Atomic Emission Spectra

• Atoms emit light at specific wavelengths.
• Each element has a unique pattern or spectrum of wavelengths.
• This unique pattern is used to identify elements.

Bohr Model and Schrödinger Model

• Bohr's model envisions electrons orbiting the nucleus in specific energy levels.
• Schrödinger's model describes electron locations in orbitals, which are regions of space where an electron is likely to be found.
• Schrödinger's model is based on wave-like properties of electrons.

Electromagnetic Radiation

• Electromagnetic waves carry energy.
• The energy of electromagnetic radiation is related to its frequency.
• Different types of electromagnetic radiation have different energies.