Cambridge International A Levels Chemistry AS (9701)
Lecture notes
CAMBRIDGE INTERNATIONAL AS LEVEL CHEMISTRY (9701) PHYSICAL CHEMISTRY NOTES
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Cambridge International A Levels Chemistry AS (9701)
Institution
Methodist College Kuala Lumpur
Excel in your AS-level Physical Chemistry studies with our specialized and concise notes! Tailored for AS-level students, these notes delve into the core principles of Physical Chemistry, providing a clear and focused understanding of essential topics. Designed with exam success in mind, our notes ...
Cambridge International A Levels Chemistry AS (9701)
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CAMBRIDGE
INTERNATIONAL AS
LEVEL CHEMISTRY
(9701) PHYSICAL
CHEMISTRY NOTES
, CHAPTER 1: ATOMIC STRUCTURE
Definitions:
• Atomic number: the number of protons in the nucleus of an atom.
• Mass number: the number of protons + neutrons in the nucleus of an atom.
• Isotopes: atoms of the same element with different mass numbers.
The Structure of an Atom:
• Every atom has nearly all of its mass concentrated in the center region
of the atom called the nucleus.
• Outside the nucleus, electrons are arranged in energy levels and
occupy regions of space called orbitals
• Protons and electrons in an atom are held together by the opposing
charges of each particle (Electrostatic attraction)
Chemical symbols:
• Every element has its own chemical symbol
Isotopes:
• Isotopes can be named by placing the nucleon number after the name.
• E.g. : C-14: carbon dating, Co-60: radiation source for cancer treatment
Ions:
• Ions are charged particles formed by the loss or gain of electron from an atom or a group
of covalently bonded atoms
, CHAPTER 2: ELECTRON IN ATOMS
Definitions:
• 1st ionization energy: the energy needed to remove 1 mole of electrons from 1 mole of
atoms of an element in the gaseous state to form 1 mole of gaseous +1 ions
• 2nd ionization energy: the energy needed to remove 1 mole of electrons from 1 mole of
+1 ions in the gaseous state to form 1 mole of gaseous +2 ions
• Atomic orbitals: regions of space that can be occupied by a maximum of two electrons
• Atomic radius: one-half the distance between two nuclei
Simple Electronic Structure:
Electrons occupy an atom according to
the capacity of the principal quantum
shell:
• Shell 1: up to 2 electrons
• Shell 2: up to 8 electrons
• Shell 3: up to 18 electrons
• Shell 4: up to 32 electrons
- A p orbital is an orbital in the p subshell
- A d orbital is an orbital in the d subshell
o s subshell contains one orbital
o p subshell contains three orbitals
o d subshell contains five orbitals
o f subshell contains seven orbitals
Electrons do not “orbit” around the nucleus:
• Misconception: Electrons move around the nucleus in a fixed orbit, like how planets move
around the Sun
• Reality: Electrons are found in an orbital which is a region of space where there is a high
probability of finding the electron
, Expanding the concept of simple electronic structure:
Electrons occupy an atom according to the capacity of the principal quantum shell:
• Shell 1:
• Shell 2:
• Shell 3:
• Shell 4:
Orbital Diagram:
• Electrons have two states, “spin” (↑ and ↓)
o There must be two electrons with opposite spins in each orbital
• Electronic configurations are based on the following principles
o Pauli Exclusion Principle: Each
orbital can hold at most 2 electrons
with opposite spins
o Aufbau Principle: Each electron is
placed from the lowest energy level
o Hund’s Rule: Every orbital in a
sublevel is singly occupied before
any orbital is doubly occupied
Writing spdf electronic configuration:
From Scandium to Zinc,
• Fill 4s orbital first, followed by 3d orbitals
o E.g. Scandium, Sc (proton number 21):
• When electrons are ionized, the 4s electrons are removed first
o E.g. Scandium(I), Sc+:
Special cases for spdf electronic configuration:
• Chromium (proton number 24):
o WRONG: 1s22s22p63s23p63d44s2
o CORRECT: 1s22s22p63s23p63d54s1 (partially filled d subshell is more stable)
• Copper (proton number 29):
o WRONG: 1s22s22p63s23p63d94s2
o CORRECT: 1s22s22p63s23p63d104s1 (fully filled d subshell is more stable)
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