EJC 2023 Atomic Structure Lecture Notes

A t o m i c S t r u c t u r e E u n o i a J u n i o r C o l l e g e 2023 JC1 H2 CHEMISTRY (9729) CORE IDEA 1 ‒ MATTER Topic 2: ATOMIC STRUCTURE Name: ________________________________________ Civics Group: _________ LEARNING OUTCOMES Students should be able to: [From the topic of Atomic Structure] (a) Identify and describe protons, neutrons and electrons in terms of their relative charges and relative masses (b) Deduce the behaviour of beams of protons, neutrons and electrons in an electric field (c) Describe the distribution of mass and charges within an atom (d) Deduce the numbers of protons, neutrons and electrons present in both atoms and ions given proton and nucleon numbers (and charge) (e) (i) Describe the contribution of protons and neutrons to atomic nuclei in terms of proton number and nucleon number (ii) Distinguish between isotopes on the basis of different numbers of neutrons present (f) Describe the number and relative energies of the s, p and d orbitals for the principal quantum numbers 1, 2 and 3 and also the 4s and 4p orbitals (g) Describe the shapes of s, p and d orbitals [knowledge of wave functions is not required] (h) State the electronic configuration of atoms and ions given the proton number (and charge) (i) Explain the factors influencing the ionisation energies of elements (see the Data Booklet) (j) Deduce the electronic configurations of elements from successive ionisation energy data (k) Interpret successive ionisation energy data of an element in terms of the position of that element within the Periodic Table [From the topic of The Periodic Table] (l) Recognise variation in the electronic configurations across a Period and down a Group (m) Describe and explain qualitatively the trends and variations in atomic radius, ionic radius, first ionisation energy and electronegativity: (i) Across a Period in terms of shielding and nuclear charge (ii) Down a Group in terms of increasing number of electronic shells, shielding and nuclear charge

A t o m i c S t r u c t u r e E u n o i a J u n i o r C o l l e g e 2 | P a g e LECTURE CONTENT 1 The Atom and the Subatomic Particles ................................ ................................ .............. 3 1.1 Subatomic Particles ................................ ................................ ................................ ............ 3 1.2 Nuclides and Isotopes ................................ ................................ ................................ ........ 3 1.3 Behaviour of Subatomic Particles in an Electric Field ................................ ......................... 5 2 The Arrangement of Electrons ................................ ................................ ............................ 8 2.1 Atomic Orbitals ................................ ................................ ................................ ................... 8 2.2 Relationship between Principal Quantum Shells, Subshells and Orbitals .......................... 10 3 Electronic Configuration ................................ ................................ ................................ ... 11 3.1 Rules for Arranging Electrons ................................ ................................ ........................... 11 3.2 Electronic Configuration of an Atom ................................ ................................ .................. 12 3.3 Electronic Configuration of Atoms and the Periodic Table ................................ ................ 15 3.4 Electronic Configuration of an Ion ................................ ................................ ..................... 16 3.5 Anomalous Electronic Configurations ................................ ................................ ............... 17 4 Factors Affecting Atomic Properties and Periodic Trends ................................ ............. 18 5 Trends in Ionisation Energies ................................ ................................ ........................... 19 5.1 Ionisation Energy (I.E.) ................................ ................................ ................................ ..... 19 5.2 Trends of 1st I.E. ................................ ................................ ................................ ............... 19 5.3 Successive I.E. of an Atom ................................ ................................ ............................... 20 6 Trends in Atomic Radius, Ionic Radius, and Electronegativity ................................ ....... 23 6.1 Trends Across the Period ................................ ................................ ................................ . 24 6.2 Trends Down the Group ................................ ................................ ................................ ... 25 6.3 More Observations About Ionic Radii ................................ ................................ ................ 25 KEY IDEAS ................................ ................................ ................................ ................................ .... 26 ANNEX 1 HISTORICAL PERSPECTIVE OF ATOMIC STRUCTURE ................................ ....... 28 ANNEX 2 ELECTRONIC CONFIGURATIONS OF D-BLOCK ELEMENTS ............................... 29 REFERENCES 1. Chemistry (for CIE AS & A Level) by Peter Cann & Peter Hughes 540 CAN 2. Chemistry: The Molecular Nature of Matter & Change by Martin S. Silberberg 540 SIL 3. Calculations in A Level Chemistry (4th Edition) by E.N. Ramsden 540 RAM 4. Calculations for AS/A Level Chemistry by Jim Clark 540 CLA

A t o m i c S t r u c t u r e E u n o i a J u n i o r C o l l e g e 3 | P a g e 1 The Atom and the Subatomic Particles 1.1 Subatomic Particles An atom is the smallest particle found in an element that can take part in a chemical reaction. Particles that are smaller than the atom are called subatomic particles. The three main subatomic particles that form an atom are protons, neutrons, and electrons. Protons and neutrons are collectively known as nucleons. The centre of the atom is called the nucleus. Particles Symbol Position in atom Relative Charge Mass / amu* Actual mass / kg Protons p Nucleus +1 1 1.67 × 10–27 Neutrons n Nucleus 0 1 1.67 × 10–27 Electrons e Orbitals −1 1 1836 9.11 × 10–31 * Atomic mass units, or amu. It is defined as 1 12 the mass of one atom of carbon-12. Almost the whole mass of the atom is concentrated in the nucleus, which takes up an extremely small space relative to the size of the whole atom. The size of an atom is easily more than 10,000 times that of the nucleus. 1.2 Nuclides and Isotopes A nuclide is an atomic species whose proton and nucleon number are specified. It is usually represented in the manner below, using fluorine, F as an example: Learning Outcome: (a) Identify and describe protons, neutrons and electrons in terms of their relative charges and relative masses (c) Describe the distribution of mass and charges within an atom Learning Outcome: (d) Deduce the numbers of protons, neutrons and electrons present in both atoms and ions given protons and nucleon numbers (and charge) (e) (i) Describe the contribution of protons and neutrons to atomic nuclei in terms of proton number and nucleon number (ii) Distinguish between isotopes on the basis of different numbers of neutrons present F 19 9 Nucleon number (A) or Mass number Nucleon number is the total number of protons and neutrons in the nucleus of an atom. Proton number (Z) or Atomic number Proton number is the number of protons in the nucleus of an atom.

A t o m i c S t r u c t u r e E u n o i a J u n i o r C o l l e g e 4 | P a g e The mass number ( A) and atomic number ( Z) give us information about the number of subatomic particles in the species. In a neutral atom, no. o