Chemistry Study Notes on Electronegativity, Atomic Radius, Metal and Nonmetal Reactivity, Ionization Energy

Electronegativity

  • Definition: Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.

  • Relationship with valence electrons (ve): The more valence electrons an atom has, the stronger its tendency to gain electrons to fulfill the octet rule.

  • Halogens: Commonly known as highly electronegative elements, halogens desire to gain one additional electron to complete their valence shell.

Atomic Radius

  • Definition: The atomic radius is a measure of the size of an atom, typically the distance from the nucleus to the outermost shell of electrons.

  • Factors affecting atomic radius:

    • More valence electrons lead to the octet being more full, which impacts the atom’s electron affinity and its size.

    • Smaller atomic radius results because valence electrons are held tighter by the nucleus due to effective nuclear charge.

  • Shielding Effect:

    • Definition: The shielding effect occurs when core electrons block the attraction of valence electrons to the nucleus, reducing effective nuclear charge felt by these electrons.

Reactivity of Metals

  • Characteristics:

    • Reactivity increases with larger atomic radius due to decreased nuclear charge.

    • A lower nuclear charge results in a weaker attraction to valence electrons, hence metals with larger sizes react more readily.

    • This effect is due to the presence of more electron shells, which results in a weaker hold on valence electrons.

Reactivity of Nonmetals

  • Characteristics:

    • Smaller nonmetals hold onto their electrons more tightly because of their higher electronegativity.

    • Smaller atomic radius means valence electrons are closer to the nucleus, making it easier for these nonmetals to gain electrons.

Ionization Energy

  • Definition: Ionization energy is the energy required to remove an electron from an atom in its gaseous state.

  • Factors influencing ionization energy:

    • Higher nuclear charge results in a stronger hold on valence electrons, increasing the energy needed to remove an electron.

    • Nonmetals tend to have high ionization energies as they want to gain electrons to fill their octet, making them hold onto their electrons more tightly.

    • Elements located higher up in the periodic table (with fewer shells) have electrons that are physically closer to the nucleus, necessitating more energy to overcome nuclear pull and remove an electron.