Polarity, Electronegativity, and Ions

Atoms and Their Components

  • Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons.
  • Protons have a positive charge, while electrons have a negative charge.
  • In a neutral atom, the number of protons equals the number of electrons, resulting in no net charge.
  • The periodic table organizes elements based on their atomic structure.
  • Oxygen has 8 protons and 8 electrons.

Electron Arrangement

  • Electrons are arranged in shells around the nucleus.
  • The first shell holds a maximum of 2 electrons.
  • The second shell holds a maximum of 8 electrons.
  • Oxygen has 2 electrons in the first shell and 6 in the second shell.

Hydrogen Atoms

  • Hydrogen is the simplest atom, having only one proton and one electron.
  • Hydrogen's single electron resides in the first shell.
  • Atoms "prefer" to have full electron shells (2 in the first shell, 8 in the second, etc.).

Water Formation (H₂O)

  • Water is formed through covalent bonding, where atoms share electrons.
  • Two hydrogen atoms share electrons with one oxygen atom.
  • Each hydrogen atom now effectively has 2 electrons in its first shell.
  • The oxygen atom now has 8 electrons in its second shell.

Polarity of Water

  • A molecule is formed when multiple atoms bond together.
  • Oxygen gas (O₂) is a molecule consisting of two bonded oxygen atoms.
  • Polarity arises from an uneven distribution of electrons within a molecule.

Electronegativity

  • Electronegativity is the tendency of an atom to attract electrons towards itself.
  • Oxygen is more electronegative than hydrogen.
  • In water, electrons spend more time near the oxygen atom, making it slightly negative.
  • The hydrogen side of the water molecule becomes slightly positive.
  • This uneven distribution of charge makes water a polar molecule.
  • Polar molecules have areas of slight positive and slight negative charge due to uneven electron distribution.

Water Molecules Interaction

  • Polar molecules bind with each other due to their positive and negative charges.
  • The negative oxygen side of one water molecule can bind with the positive hydrogen side of another water molecule.
  • This is called hydrogen bonding.

Hydrophilic Molecules

  • Polar molecules are hydrophilic (water-loving) because they dissolve in water.
  • Glucose (sugar) is a polar molecule with hydroxyl groups (OH) that exhibit positive and negative charges.
  • When glucose is mixed with water, it dissolves because the positive and negative sides of glucose molecules interact with the positive and negative sides of water molecules.

Ions vs. Polar Molecules

  • Sodium (Na) atom: Has 11 protons and 11 electrons.
  • Electron Configuration: 2 electrons in the first shell, 8 in the second, and 1 in the third.
  • Chlorine (Cl) atom: Has 17 protons and 17 electrons.
  • Electron Configuration: 2 electrons in the first shell, 8 in the second, and 7 in the third.
  • Chlorine has a strong tendency to gain one more electron to complete its third shell.
  • Na readily gives up its single electron; Chlorine has a high affinity for an additional electron.

Ion Formation

  • When sodium and chlorine interact, chlorine takes the electron from sodium.
  • This results in the formation of a sodium ion (Na^+) and a chloride ion (Cl^-).
  • Ions have an uneven distribution of electrons, resulting in a net charge.