Chemical Bonding GCSE Notes

Ionic Bonding 

• A metal (eg: Calcium) and nonmetal (eg: Chlorine) react together (join a relationship in a way) 

  • The metal will lose its electrons and will become a cation (+)

  • The non-metal will gain its electrons and will become a anion (-)

    • Because these charges are complete opposite, strong forces of attraction will occur here →this is ionic bonding 

Source: https://www.chemistrylearner.com/chemical-bonds/ionic-bond 

Covalent Bonding 

• These solely involve non-metals (they are the ones that gain electrons in ionic bonding) 

• Instead of giving and gaining electrons, these atoms prefer to share electrons (like a bag of chips) 

• The covalent bond forms because of the electrostatic attraction between 2 things: 

  • Attraction of positive nuclei (plural word for nucleus) between bonded atoms

    • Reminder: The nucleus is the “core” of the atom, a dense region with electrically neutral neutrons and electrically positive protons (electrons are on the outside)

  • Shared electrons between them 

• Atoms only share electrons with their outermost shells (suprise suprise…valence electrons!)

• Covalent bonds can produce a single bond, double or triple bond between atoms 

Source: https://www.chemistrylearner.com/chemical-bonds/covalent-bond/single-covalent-bond 

Coordinate Bonding 

• Same as a covalent bond in concept, however the electrons that will be shared come from the same atom

• Purely ionic or purely covalent bonds are not common, many bonds fall in between of these two extremes 

  • Say hi to what is known as “polar bonds” 

  • Polarity is based on electronegativity, and the higher the difference in electronegativity between the two atoms, the higher their “ionic character” (very iconic of these atoms!)

• Example: H₂O + H⁺ (water and hydrogen ion) → H₃O (same atom is hydrogen) 

Electronegativity and Polarity 

• Electronegativity is in other words “the rizz of the atom” 

  • It is the measure of how strongly atoms attract electrons in a covalent bond 

    • The electron pair is not shared evenly 

    • Bonding electrons are pulled closer to the electronegative atom 

    • There will be an atom that is slightly more negative and an atom that is slightly more positive 

    • If two atoms have the same amount of “rizz” or electronegativity, then they will be non-polar 

    • How do you determine this? It’s called the “rizz test” (aka electronegativity difference test)

      • If the electronegativity difference between the two atoms are less than 0.4 →nonpolar covalent bonds (platonic friends) 

      • If the electronegativity difference between the two atoms are greater than 0.4 or less than 1. →polar covalent bonds (one person is crushing) 

      • If the electronegativity difference between the two atoms is greater than 2 →ionic bonds (they are dating!)

Source: https://www.chemistrylearner.com/the-periodic-table/electronegativity 

Dipole-Dipole Forces 

• Polar molecules (they are formed based on polar covalent bonds or ionic bonds between atoms) have dipoles 

  • Dipoles are little flags that alert if a part of the molecule has a slightly negative or positive charge (because of the difference in electronegativities) 

  • When the molecules arrange themselves so that the negatively and positively charged regions are close to each other, there will be an attraction between them 

Source: https://www.chemistrylearner.com/chemical-bonds/dipole-dipole-forces 

Induced Dipole-Induced Dipole Forces 

• Molecules with no dipole can still have intermolecular bonding, this is because temporary dipoles are formed (based on the constant motion of electrons 

• These induced forces can increase when the number of electrons in a molecule will increase as well 

  • Higher electron numbers = greater fluctuation in the electron cloud around the nuclei = larger temporary and induced dipoles created = stronger forces between molecules = van der Waals forces

Source: https://www.chemistrylearner.com/chemical-bonds/van-der-waals-forces

Hydrogen Bonding 

• Special type of intermolecular forces (not an actual bond where electrons are shared) that happens with molecules that have hydrogen, specifically hydrogen that is bonded to Flourine, Oxygen and/or Nitrogen

  • This three pair are very electronegative and when bonded with a small hydrogen atom, there is a high charge density 

• Hydrogen bonding increases boiling point →more heat is needed to break the forces

• Hydrogen bonding increases solubility →covalent compounds can replace current hydrogen bonds by forming new ones with the water 

Source: https://www.chemistrylearner.com/chemical-bonds/hydrogen-bond