1.4- Bonding Flashcards
(a)
Ionic bonding
Ionic bonding occurs when a metal and a non-metal react. The metal loses electrons to form a positively charged cation (+), while the non-metal gains electrons to form a negatively charged anion (-). These oppositely charged ions are held together by strong electrostatic forces of attraction.
(b)
Covalent bonding
Covalent bonding occurs when non-metals bond by sharing electrons in their outer shells. Each atom donates one electron to form a bond pair with opposite spins. The bond is held together by the electrostatic attraction between the positive nuclei of the bonded atoms and the shared electrons.
(b)
Coordinate bonding
The same as a covalent bond but both electrons forming the bond pair come from the same atom.
(c)
intermediate character of many bonds between purely ionic and purely covalent
Most bonds are polar, meaning they have both ionic and covalent character. The bigger the electronegativity difference between atoms, the more ionic the bond is. A smaller difference means the bond is more covalent.
(d)
Electronegativity
Electronegativity measures how strongly an atom attracts electrons in a covalent bond. The higher the electronegativity, the greater the atom’s ability to attract bonding electrons.
(d)
Bond polarity
In a covalent bond, electrons are often shared unevenly due to differences in electronegativity. The more electronegative atom becomes δ⁻ (slightly negative), and the other becomes δ⁺ (slightly positive), forming a polar bond. f both atoms have equal electronegativity, the bond is non-polar because electrons are shared equally.
(d)
Bond polarity (2)
If the electronegativity difference is:
< 0.4 → Non-polar covalent
0.4 to ~1.9 → Polar covalent
≥ 2.0 → Ionic bond
The greater the difference, the more ionic the bond becomes.
(e)
forces between molecules being much weaker than covalent (and ionic) bonds
Intermolecular forces are much weaker than covalent and ionic bonds. While covalent and ionic bonds involve strong attractions within molecules or between ions, intermolecular forces are weak attractions between molecules.
(f)
Dipole-dipole forces
Polar molecules have dipoles – one end is δ⁺ and the other δ⁻ due to different electronegativities. When dipoles align, the negative end of one molecule is attracted to the positive end of another. This creates an intermolecular attraction between them.
(f)
Induced dipole-induced dipole forces
Electrons are always moving, causing temporary dipoles from uneven distribution. These can induce dipoles in nearby molecules, creating van der Waals forces (induced dipole–induced dipole). The more electrons a molecule has, the stronger these forces become, increasing intermolecular attraction.
(g)
Hydrogen bonding
Hydrogen bonding occurs when hydrogen is bonded to fluorine, oxygen, or nitrogen – very electronegative atoms. This creates a δ⁺ hydrogen with high charge density, which attracts a lone pair on another electronegative atom in a different molecule. The hydrogen is covalently bonded to one atom and hydrogen-bonded to another.
(g)
Effects of hydrogen bonding
Hydrogen bonding increases boiling points because it takes more energy to overcome these stronger intermolecular forces compared to van der Waals forces.
It also increases solubility—substances that can form hydrogen bonds with water can dissolve by replacing water’s existing hydrogen bonds.
(h)
VSEPR principle and its use in predicting the shapes of simple molecules and ions
Molecular shape is determined by the repulsion between electron pairs around the central atom. Lone pairs repel more strongly than bonding pairs, following the order: lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair. This repulsion affects bond angles and molecular geometry.
(i)
Name the shape of BeCl2. What is the bond angle?
Linear
Angle= 180 °
(i)
Name the shape of BCl3. What is the bond angle?
Trigonal planar
Angle= 120°
(i)
Name the shape of CH4. What is the bond angle?
Tetrahedral
Angle = 109.5°
(i)
Name the shape of NH3. What is the bond angle?
Trigonal pyramidal
Bond angle = 107°
(i)
Name the shape of NH4+ . What is the bond angle?
Tetrahedral
Bond angle = 109.5
(i)
Name the shape of H2O. What is the bond angle?
Bent
Bond angle = 104.5°
(i)
Name the shape of SF6. What is the bond angle?
Octahedral
Bond angle = 90°
