Topic 2 + 3 + 4 Flashcards
2. The covalent bond, the molecular geometry of inorganic molecules (e.g. carbon monoxide, carbon dioxide, ammonia). Ionization energy, electron affinity, electronegativity. The ionic bond, hydrox- ylapatite and fluoroapatite 3. The structures of polyatomic ions, the complexes 4. The secondary bonds and interactions between molecules
What is Ionization energy (IE)?
Minimum energy required to remove an electron from a gaseous atom or ion when the atom or ion is in its ground state (unit: kJ/mol)
(always positive - energy is needed).
Unit of Ionization energy (IE)?
kJ/mol
Trends of Ionization energy (IE)?
Ionization energy (IE1) generally increases
- from left to right across a period,
- up a group (smaller atoms are more difficult to ionize).
What is Electron affinity?
Energy change that occurs when electron is added to a gaseous atom (unit: kJ/mol) (can be negative, positive or zero; stable anion can be formed if EA is negative - energy is released upon electron uptake).
Element(g) + e− → Element−(g) energy change = EA
Which atom has the largest Electron affinity?
What is the benefit for this feature?
Chlorine has the largest (negative) EA
Addition of an e- to a chlorine atom releases the greatest amount of energy.
Describe trend of electron affinity.
Electron affinity (EA) generally increases
- from left to right across a period,
- up a group (smaller atoms are more difficult to ionize).
(similar trends as the first ionization energy)
Are there any exceptions to trend of electron affinity
Electron affinity (EA) generally increases
- from left to right across a period,
- up a group (smaller atoms are more difficult to ionize).
(similar trends as the first ionization energy)
Which bond is created between non-metals and non-metals? Give an example
COVALENT
(e.g. CO2)
Which bond is created between metals and nonmetals?
IONIC
(e.g. NaF)
Which bond is created between metals and metals?
METALIC
(e.g. Ag-Hg amalgam)
Which bond is created between Hydrogen atom and nonmetals?
COVALENT
(e.g. HCl)
What is covalent bonding?
a primary bond based on electron sharing between two atoms.
Describe the double bond
4 bonding electrons
→ a σ [sigma] and a π [pi] bonding molecular orbitals are filled
Describe triple bond
Six bonding electrons: triple bond
=> a σ [sigma] and two π [pi] bonding molecular orbitals are filled
Describe molecular geometry and name of this molecule.
VSERP - Tetrahedral - 4 bond pairs, no lone pairs
Name - Methane (CH4)
Describe molecular geometry and name of this molecule.
VSERP - Trigonal-pyramidal - 3 bond pairs, 1 lone pair
Name - Ammonia NH3
Describe molecular geometry and name of this molecule.
VSERP - Bent - 2 lone pairs, 2 bond pairs
Name - Water H2O
Describe molecular geometry and name of this molecule.
VSERP - Linear - 1 lone pair, 3 bond pairs
Name - Carbon monoxide CO
What is Overall dipole moment?
a vectorial sum of all bond dipoles in the molecule
Is a molecule containing polar bonds a polar molecule?
NO!
For a polar molecule, the overall dipole moment must NOT be ZERO.
For a non polar molecule → overall dipole moment is ZERO
Is CCl4 a polar molecule?
NO. Overall dipole moment is ZERO
What is Ionic bonding?
primary bond formed between oppositely charged ions due to mutual electrostatic attraction.
What are Ionic compounds (salts)?
lattices of undefined number of ions.
=> Their formula unit is the lowest whole number ratio of the ions (e.g. NaCl, MgCl2).
An example of polyatomic ion
Sulfate ion
3 types of ion that enamel is made form
calcium ions (Ca2+),
phosphate ions (PO4 3-)
hydroxide ions (OH-)
→ The formula for this material is Ca10(PO4)6(OH)2,
What is Hydroxyapatite?
The material made from….
- calcium ions (Ca2+),
- phosphate ions (PO4 3-)
- hydroxide ions (OH-)
→ The formula for this material is Ca10(PO4)6(OH)2,
Which process that Hydroxyapatite is created?
mineralization
→ Ca2+, PO4 3-, and OH- ions in the saliva solution are recombining to deposit enamel back on the teeth
What is Fluoroapatite?
The material made from….
- calcium ions (Ca2+),
- phosphate ions (PO4 3-)
- fluoride ion (F)
→ The formula for this material is Ca10(PO4)6F2
How is Fluoroapatite created? (tooth enamel)
Fluoride ion (F) exchanges with hydroxide ion in the hydroxyapatite structure
=> tooth enamel is strengthened
=> produces an enamel that is less soluble in acidic medium
What is an intermolecular force?
an attractive force that acts between a molecule and another molecule.
What are the three main types of intermolecular force?
dipole–dipole interactions, hydrogen bonds, and London forces.
What is dipole–dipole interaction?
- Occur between POLAR molecule
- (+) Positive end attracts (-) negative end
- Strengthen depends on the extent of molecular polarity
What is Hydrogen bond?
hydrogen-containing molecules in which
→ hydrogen is covalently bonded to a highly electronegative element which can be fluorine, oxygen and nitrogen
What are London Forces?
A weak temporary intermolecular force that occurs between an atom or molecule (polar or nonpolar) and another atom or molecule (polar or non- polar).
The type of bond that occur between non polar molecules
A weak temporary intermolecular force that occurs between an atom or molecule (polar or nonpolar) and another atom or molecule (polar or non- polar).
What are hydrophobic interaction?
Interactions that result when two nonpolar side chains are close to each other.
