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Chemistry > Chapter 6 - Bonding and structure > Flashcards

Chapter 6 - Bonding and structure Flashcards

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1
Q

What is ionic bonding ?

A

Ionic bonding is the electrostatic attraction between oppositely charged ions

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2
Q

What is covalent bonding ?

A

Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

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3
Q

What is the electron pair repulsion theory ?

A

It explains and predicts the shapes of molecules and polyatomic ions

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4
Q

What is the order of pair repulsion, strongest to weakest?

A
  • Lone-Lone
  • Bonded-Lone
  • Bonded-Bonded
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5
Q

What is a lone pair of electrons ?

A
  • A lone pair refers to a pair of electrons that are not shared with another atom in a covalent bond
  • Lone pairs repel more strongly compared to bonding pairs
  • Every lone pair decreases the bond angle by 2.5 degrees
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6
Q

What shape is a molecule with no lone pairs ?

A
  • Tetrahedral, 109.5 degree bond angle

- For example, CH4

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7
Q

What shape is a molecule with one lone pair ?

A
  • Trigonal pyramidal, 107 degree bond angle

- For example, NH3

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8
Q

What shape is a molecule with two lone pairs ?

A
  • Non-linear, 104.5 degree bond angle

- For example, H2O

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9
Q

What shape is a molecule with two bonded pairs ?

A
  • Linear, 180 degree bond angle

- For example, CO2

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10
Q

What shape is a molecule with three bonded pairs ?

A
  • Trigonal planar, 120 degree bond angle

- For example, BF3, boron trifluoride

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11
Q

What shape is a molecule with four bonded pairs ?

A
  • Tetrahedral, 109.5 degree bond angle

- For example, CH4

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12
Q

What shape is a molecule with five bonded pairs ?

A
  • Trigonal Bipyramidal

- There are actually two bond angles, 120 degrees in one plane and 90 degrees in another plane

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13
Q

What shape is a molecule with 6 bonded pairs ?

A
  • Octahedral, 90 degree bond angles

- For example, SF6 Sulfur hexafluoride

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14
Q

Carbonate ion

A

CO3 (2-), Trigonal Planar, 120 degree bond angles

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15
Q

Nitrate ion

A

NO3(-), Trigonal planar, 120 degree bond angles

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16
Q

Sulfate ion

A

SO4(2-), tetrahedral, 109.5 degree bond angles

17
Q

What is electronegativity ?

A

The ability of an atom to attract the bonding electrons in a covalent bond

18
Q

How is electronegativity measured ?

A
  • It is measured on the Pauling scale
  • A higher value on the Pauling scale means it has higher electronegativity and thus a greater attraction for an electron pair in a covalent bond
19
Q

What do Pauling values depend on ?

A
  • Depends on an elements position in the table
  • Across the periodic table, the nuclear charge increases and the atomic radius decreases
  • As you go up and across the table, the values increase
20
Q

Covalent or ionic

A
  • Covalent bonds have an electronegativity difference of 0
  • Polar covalent bonds have an electronegativity difference between 0 and 1.8
  • Ionic bonds have an electronegativity difference of more than 1.8
21
Q

What makes a bond polar ?

A
  • Two atoms with an electronegativity difference of at least 0.5, the bonding electrons are pulled more towards the more electronegative atom
  • A polar bond forms a dipole
22
Q

How is a dipole formed ?

A
  • A difference in charge between the two atoms

- A dipole in a polar covalent bond is a permanent dipole

23
Q

What happens if the polar bonds are arranged symmetrically in a molecule ?

A

The dipoles cancel each other out, so the molecule has no overall dipole and is non polar

24
Q

What happens if the polar bonds are arranged unsymmetrically in a molecule ?

A

Uneven distribution of charge and the molecule will have an overall dipole

25
Q

What are the three types of IMFs ?

A
  • Induced dipole dipole interactions AKA London Forces
  • Permanent dipole dipole interactions
  • Hydrogen bonding
26
Q

What are London Forces ?

A
  • Weak IMFs that exist between all molecules, polar or non polar
  • They act between induced dipoles in different molecules, only temporary dipoles
27
Q

How do induced dipoles come around ?

A
  • Movement of electrons produces a changing dipole in a molecule
  • An instantaneous dipole will exist, but its position will be changing
  • The instantaneous dipole induces a dipole in a neighbouring molecule
  • The induced dipole induces further dipoles on neighbouring molecules, which then attract more and more
28
Q

What effect does the amount of electrons have on boiling point?

A
  • The more electrons
  • The larger the instantaneous and induced dipoles
  • The greater the induced dipole dipole reactions
  • The stronger the London forces
  • The higher their boiling point
29
Q

What are Permanent dipole dipole interactions ?

A
  • Permanent dipole dipole interactions act between the permanent dipoles in different polar molecules
  • The delta negative part in one molecule is attracted to the delta positive part in another molecule
30
Q

How much energy is required to break permanent dipole-dipole interactions ?

A
  • More energy is required as it is stronger than London forces.
  • If you have permanent dipoles you are likely to also have London forces
31
Q

What is the MP and BP like for simple molecular substances ?

A

They have a low melting and boiling point, this is due to the fact that a little bit of energy is required to break the weak IMFs

32
Q

What is the solubility of Non-Polar Simple Molecules like in non polar solvent ?

A
  • IMFs form between the two
  • Interactions weaken the IMFs in the lattice
  • IMF breaks and the compound dissolves
33
Q

What is the solubility of Non-Polar Simple Molecules like in polar solvents ?

A
  • There are little interactions between molecules in the lattice and in the solvent
  • Bonding within the polar solvent is too strong to be broken
34
Q

What is the solubility of Polar Simple Molecules like ?

A

Polar covalent substances may dissolve in polar solvents. This is due to the fact that the polar solute molecules and the polar solvent molecules can attract each other

35
Q

How do intermolecular forces explain simple covalent compounds not conducting electricity?

A

Covalent molecules are uncharged as the permanent dipoles are not strong enough. This means they can not carry charge.

36
Q

What is Hydrogen Bonding ?

A
  • Hydrogen bonding is the intermolecular bonding between the lone pair of electrons in molecules containing N, O or F and a H atom
  • It acts between a lone pair of electrons and a hydrogen in a different molecule
37
Q

What are some anomalous properties of water ?

A
  • Ice is less dense than water
  • Water has a high MP and BP
  • It has a high surface tension
  • Water has a high viscosity
38
Q

Why is ice less dense than water ?

A
  • In ice, water molecules are held together in an open tetrahedral lattice that is full of holes
  • When ice melts, hydrogen bonds are broken, so ice has more of these than water. As hydrogen bonds are long, this causes ice to be less dense than water.
39
Q

Why does water have a high MP and BP ?

A

Water has both London forces and hydrogen bonds which mean more energy is needed to break these bonds.

Chemistry (29 decks)

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