Lesson 4

• Electronegativity is a measure of how strongly atoms attract bonding electrons to themselves. The higher the electronegativity, the greater an atom’s attraction for electrons.
• Covalent Compounds are molecules that form when two different atoms form a covalent bond. They typically have similar electronegativity and are non-metals.
• Matter is anything that takes up space and can be weighed. In other words, matter has volume and mass.
• Covalent Compound

  Electrons shared between atoms
• John Newland’s Law of Octaves: He arranged all the elements known at the time in order of their atomic masses, noting that the eighth element has similar properties to that of the first element, the ninth to the second, and the tenth to the third. He called this pattern the Law of Octaves.
• Ionic Compounds are crystalline solids formed by neatly packed ions of opposite charge. They are usually formed when metals react with non-metals.
• Compound


  A substance that is made up of two or more different elements that are chemically joined. For example, water.
• Types of Compounds

  • Ionic Compounds
  • Covalent Compounds
• Element


  A substance made up entirely of one type of atom. They are considered to be pure substances. For example, the element Gold.
• Lewis Dot Symbol/Structure


  Lewis structures represent the valence electrons of atoms within a molecule, helping visualize the valence electrons of atoms and molecules, whether they exist as lone pairs or within bonds.
• Valence electrons are electrons located in the outermost electron shell of an atom. These electrons participate in bonds and reactions, determining reactivity, electronegativity, and the number of bonds an element can form.
• Molecule


  A substance that contains two or more atoms, from the same element, which are chemically joined. For example, hydrogen molecule.
• Atom


  The smallest part of a matter that has all the characteristics of a chemical element. An atom consists of sub-atomic particles called protons, neutrons, and electrons.
• Ionic Compound


  Complete transfer of electrons from one atom to another
• Factors Affecting the Electronegativity of an Atom: Hybridization State of an Atom
• The higher the electronegativity, the greater an atom’s attraction for electrons
• The higher the effective nuclear charge means that the electronegativity is also high
• Factors Affecting the Electronegativity of an Atom: Oxidation Number
• Lewis structures


  Diagrams that represent the valence electrons of atoms within a molecule
• The number of covalent bonds present between two bonded atoms is known as the bond order
• Factors Affecting the Electronegativity of an Atom: Atomic Size or Radius
• Electronegativity increases with increasing s-character of the hybrid orbital
• Choose the element whose valence electrons would experience the greatest shielding effect: Arsenic, Antimony, Bismuth
• Factors Affecting the Electronegativity of an Atom: Effective Nuclear Charge
• Types of Chemical Bond based on Electronegativity Difference

  • Ionic
  • Polar Covalent
  • Non-Polar Covalent
• The more core electrons means the greater shielding effect
• Factors Affecting the Electronegativity of an Atom: The Shielding Effect
• Since electronegativity is relative, it has no unit of measurement
• The electronegativity of an element is the tendency for the nucleus of the atoms of elements to attract electrons when they are chemically combined with the atoms of another element
• The electronegativity value increases with the increase in oxidation number
• Atomic radius generally decreases as you move from left to right across a period and increases as you move down a group
• Electronegativity is a measure of how strongly atoms attract bonding electrons to themselves
• With the increase in bond order, the bond distance decreases thus increasing the effective nuclear charge which results in the increase of electronegativity
• The value of electronegativity of an element describes the ability of its atom to compete for electrons with another atom to which it is bonded
• Factors Affecting the Electronegativity of an Atom: Bond Order
• Linus Carl Pauling: 'PAULING SCALE OF ELECTRONEGATIVITY'
• Types of Chemical Bond based on Electronegativity Difference

  • Ionic: ∆EN ≥ 1.7
  • Polar Covalent: 1.7 > ∆EN > 0.4
  • Non-Polar Covalent: ∆EN ≤ 0.4
• Try This!
• 1.4 is Polar Covalent
• 0 is Non-Polar Covalent