Atomic Structure Notes (Grade A)

Summary:

These chemistry notes cover various topics, including the atomic structure and molecules, isotopes, isobars, isotones, and Pauli’s exclusion principle. The shape of atomic orbitals is also discussed, including the shape of s-orbitals, p-orbitals, and d-orbitals. The four quantum numbers are explained, including the principal, azimuthal, magnetic, and spin quantum numbers. The dual nature of matter is also briefly mentioned. The electronic configurations of atoms are covered, including the Aufbau principle and Hund’s rule.

Excerpt:

ATOMIC STRUCTURE

ATOMS- The word atom is a Greek word meaning indivisible an ultimate particle that cannot be further
subdivided.

“An atom is the smallest particle of an element that can exist independently and retain all its”.

Atom is made up of electrons, protons, and neutrons.

MOLECULAR E- “A molecule is the smallest part of an element or a compound that can have a stable and independent existence.”

➢ PROTON- “A Proton is a subatomic particle found in the nucleus of every atom”. Ernest Rutherford is
credited with the discovery of the proton in 1920.
➢ ELECTRON- “ An atom is a negatively charged subatomic particle.” J.J. Thomson is credited with the
discovery of electrons in 1897.
➢ NEUTRON- “A neutron is a subatomic particle found in the nucleus of every atom except that of simple
hydrogen”.James Chadwick is credited with the discovery of neutrons in 1932.

ATOMIC NUMBER-The total number of protons present in the nucleus of an atom of an element expresses its atomic number(z).
➢ ISOTOPES –Isotopes are different atoms of the same element which have the same atomic number but a different mass number.
➢ ISOBARS- Atoms of different elements having the same mass number are known as isobars.
➢ ISOTONES – Nuclei having the same number of neutrons are known as isotones.

PAULI’S EXCLUSION PRINCIPLE –In 1925, Pauli presented a principle that controls the assignment of values to the quantum numbers of an electron in an orbital.” No two electrons in an atom can have the same set of all the four quantum numbers”.