Topic 1:Atomic Structure and the Periodic Table

• Outer shell electronic configuration of p-block elements: s2 p1 or s2p6
• Reason behind Chromium and copper donating one of their 4s electrons to the 3d subshell: It is more stable with a full or half-full d subshell
• Example of a configuration for s and p block ions up to Z = 36:

  • Ca: 1s2 2s2 2p6 3s2 3p6 4s2
  • Ca2+: 1s2 2s2 2p6 3s2 3p6 4s2
• Elements can be classified as s, p, and d-block elements
• Electronic configuration determines the chemical properties of an element
• Electronic configuration of s-block elements: 1 or 2 outer shell electrons
• 1. block elements can easily lose electrons to form positive ions with an inert gas configuration
• Electronic configuration of p-block elements: 1, 2, or 3 electrons can be gained to form negative ions with an inert gas configuration
• When groups 4 to 7 share electrons, they form covalent bonds
• Inert gases in Group 0 have a completely filled s and p subshells and do not need to gain, lose, or share electrons
• Transition metals in the D block tend to lose s and d electrons to form positive ions
• Periodicity is the repeating pattern of physical or chemical properties across a period
• Bond strength affects the melting and boiling points across a period, with metallic bonds getting stronger due to an increasing number of delocalized electrons and decreasing radii
• Melting and boiling points of Na, Mg, and Al are determined by metallic bonding and the increasing number of delocalized electrons
• Si has a giant covalent lattice structure with many strong covalent bonds, resulting in a very high melting/boiling point
• Melting/boiling points of P4(s), S8(s), and Cl2(g) are determined by the strength of London forces between their molecules
• Sulfur has a higher melting/boiling point compared to others in its group due to more electrons leading to stronger London forces
• Inert gases like argon are monoatomic and have the lowest melting/boiling point due to very weak London forces
• Ionisation energy is based on given data or recall of the plots of ionisation energy versus atomic number
• Jump in ionisation energy between the 2nd and 3rd ionisation energies of an element is due to the fifth electron being in an inner shell closer to the nucleus and attracted more strongly
• Ionisation energy data is provided for KJ 590 1150 4940 6460 8120 mol-1
• An element with a big jump between the 2nd and 3rd ionisation energies must be in group 2 of the periodic table
• Three main sub-atomic particles in an atom: Protons, neutrons, and electrons
• Protons are located in the nucleus
• Relative charge of an electron: -1
• Relative mass of a neutron: 1
• Atomic (proton) number is the number of protons in the nucleus
• Mass number is the total number of protons and neutrons in the atom
• Number of neutrons can be determined by subtracting the atomic number from the mass number (Number of neutrons = A - Z)
• Isotopes are atoms with the same number of protons but different numbers of neutrons
• Relative isotopic mass is the mass of one atom of an isotope compared to one twelfth of the mass of one atom of carbon-12
• Relative atomic mass is the average mass of one atom compared to one twelfth of the mass of one atom of carbon-12
• Relative molecular mass is the average mass of a molecule compared to one twelfth of the mass of one atom of carbon-12
• Relative formula mass is the sum of the relative atomic masses of the atoms in the formula
• Mass spectrometry is used to determine the isotopes present in a sample and calculate the relative atomic mass of elements
• Relative atomic mass is calculated from relative abundance of isotopes using the formula: R.A.M = (isotopic mass x relative abundance) / total relative abundance
• Mass spectrometry can be used to determine the relative molecular mass of a molecule by measuring the m/z value for the molecular ion, M+
• The largest m/z peak in a mass spectrum is due to the complete molecule and is equal to the relative molecular mass of the molecule
• Two isotopes of chlorine are Cl35 and Cl37
• Relative peak heights in the mass spectrum of diatomic molecules like chlorine can be determined by expressing the relative abundances as decimals and calculating the ratios