1.3 Bonding Flashcards
What is ionic bonding?
Electrostatic attraction between oppositely charged ions formed by electron transfer.
Why does MgO have a higher melting point than NaCl?
Mg²⁺ and O²⁻ are smaller and have higher charges than Na⁺ and Cl⁻, leading to stronger electrostatic forces.
Why are positive ions smaller than their atoms?
They have fewer electron shells and a higher proton-to-electron ratio, increasing attraction.
What trend is seen in ionic radius across a period?
It decreases due to increasing nuclear charge attracting electrons more strongly.
What is a covalent bond?
A shared pair of electrons between atoms.
What is a dative covalent bond?
A shared pair of electrons where both electrons come from the same atom.
Give an example of a molecule with a dative covalent bond.
NH₄⁺, H₃O⁺, NH₃BF₃
What is metallic bonding?
Electrostatic attraction between positive metal ions and delocalised electrons.
What factors affect metallic bond strength?
Number of protons, number of delocalised electrons, and ion size.
Why does Mg have stronger metallic bonding than Na?
Mg has more delocalised electrons, a smaller ion, and a greater nuclear charge.
What types of bonding structures exist?
Ionic, Simple Molecular, Macromolecular, and Metallic.
Why do simple molecular substances have low melting/boiling points?
They have weak intermolecular forces.
Why do metals conduct electricity?
They have delocalised electrons that move freely through the lattice.
What is the bond angle in a tetrahedral molecule?
109.5°
What is the shape and bond angle of NH₃?
Trigonal pyramidal, 107°
What causes deviations in bond angles?
Lone pairs repel more than bonding pairs.
State the steps to explain molecular shape.
Count bonding/lone pairs → electron pairs repel → lone pairs repel more → determine shape & angle.
What is electronegativity?
The ability of an atom to attract electrons in a covalent bond.
What happens when electronegativity difference is large (>1.7)?
The bond is likely ionic.
What makes a molecule polar?
Asymmetry and significant electronegativity difference between atoms.
Why is CO₂ non-polar despite polar bonds?
It is symmetrical, so dipoles cancel out.
What are Van der Waals forces?
Temporary dipoles inducing dipoles in neighbouring molecules.
What increases Van der Waals strength?
More electrons and greater molecular surface area.
What are permanent dipole-dipole interactions?
Forces between polar molecules due to permanent dipoles.
When does hydrogen bonding occur?
Between H and F, O, or N with lone pairs.
Why does H₂O have a higher boiling point than H₂S?
H₂O forms hydrogen bonds; H₂S does not.
Why do long chain alkanes have higher boiling points than branched ones?
They have more surface contact, increasing Van der Waals interactions.
What are the four crystal types?
Ionic, Metallic, Molecular, Macromolecular.
Describe diamond’s structure.
Tetrahedral with 4 strong covalent bonds per carbon atom.
Why does graphite conduct electricity?
It has delocalised electrons between layers.
Why is ice less dense than water?
Hydrogen bonds hold molecules in a structure with more space.
