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Chemistry AS > Bonding And Structure > Flashcards

Bonding And Structure Flashcards

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1
Q

What is ionic bonding?

A

It is the electrostatic attraction between oppositely-charged ions

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2
Q

Describe an ionic lattice

A

A structure containing billions of ions in 3D

-each ion is surrounded by oppositely charged ions

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3
Q

Why do most ionic compounds have high melting and boiling points?

A
  • high temps are needed for energy needed to overcome the strong electrostatic attraction between the ions
  • higher charges results in higher MP as there are more attractions from more charges
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4
Q

Why are ionic compounds soluble in polar solvents e.g water?

A
  • polar water molecules are able to break down the lattice and surround each ion in solution
  • however with ionic c’s that have large charges, the ionic attraction may be too strong for water to be able to break down. So the compound won’t be soluble
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5
Q

What 2 main processes does solubility require?

A
  • ionic lattice must be broken down
  • water molecules must attract and surround the ions
  • depends on the relative strengths of the attractions between ions and water molecules
  • solubility sometimes decreases as ionic charge increases
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6
Q

How do ionic compounds conduct electricity?

A

-when solid the ions are in a fixed position in the lattice with no mobile charge carriers
However when in liquid/dissolved in water:
-the solid ionic lattice breaks down
-the ions are now free to move as MBC’s

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7
Q

What are the main properties of ionic compounds?

A
  • High MP&BP
  • soluble in polar solvents
  • conduct electricity in liquid and aqueous
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8
Q

What is covalent bonding?

A

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

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9
Q

What is a molecule?

A

The smallest part of a covalent compound that exists while retaining the chemical properties of the compound

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10
Q

What is a dative covalent bond?

A

A CB where the shared pair of electrons has been supplied by only 1 of the bonding atoms

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11
Q

Describe the electron pair repulsion theory

A
  • electron pairs surrounding the central atom determine its shape
  • electrons repel one another (both neg,) so are as far apart as poss
  • new arrangement of electrons minimises repulsion and holds the bonded atoms in a definite shape
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12
Q

Why do lone pairs repel more strongly than bonded pairs?

A

They are closer to the central atom and occupy more space

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13
Q

What happens with the shapes with 4 electron pairs? Etc H20, and CH4

A
  • the electron pair around the central atom repel eachother as far as possible
  • lone pairs repel bonded pairs closer together as they repel more strongly. This decreases the bond angle
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14
Q

Why is there an octohedral shape from 6 bonded pairs?

A

E.g Sf6

  • the 6 fluorine atoms are positioned at the corners of an octahedron
  • makes up an octohedral shape
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15
Q

What is electronegativity?

A

The attraction of a bonded atom to a pair of electrons in a covalent bond

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16
Q

When is a bond non polar?

A
  • the bonded atoms are the same
  • the bonded atoms have similar EN
  • the bonded electron pair is shared equally between the bonded atoms
17
Q

What is a polar bond?

A
  • when the bonded electron pair is shared unequally between the bonded atoms
  • polar when bonded atoms are different and have different EN values
18
Q

What is a dipole?

A

Separation of opposite charges

19
Q

Why is CO2 non polar?

A

The 2 dipoles exactly oppose eachother so the dipoles cancel eachother

20
Q

What are intermolecular forces?

A

Weak interactions between dipoles of different molecules

21
Q

Explain what an induced dipole is

A
  • movements of electrons produces a changing dipole in a molecule
  • then an instantaneous dipole exists with a constant shiftin position
  • the ID induces a dipole on a neighbouring molecule
  • the induced dipole induces further dipoles which attract one another
22
Q

What is a London force?

A

A weak intermolecular force that exists between all molecules

23
Q

Induced dipoles

The more electrons…

A
  • the larger the induced and instantaneous dipoles
  • greater the induced dipole-dipole interactions
  • the stronger the attractive forces
24
Q

What is a simple molecular substance?

A

-made up of simple molecules e.g Neon, H, CO2&H20

25
Q

Describe a simple molecular lattice

A
  • solid state
  • molecules held in place by weak intermolecular forces
  • atoms within each molecule are bonded strongly by covalent bomds
26
Q

Simple molecular low MP&BP

A
  • weak forces can be broken by energy present at low temps

- when it is broken apart during melting only the weak intermolecular forces break and the strong covalent bonds remain

27
Q

Solubility of simple molecular structures (non-polar)

A
  • intermolecular forces form between the solvent&molecules
  • interactions weaken the intermolecular forces so they break&compound dissolves
28
Q

Simple molecular solubility in polar solvents

A

There is little interaction between the molecules in the lattice and solvent
-molecule is too strong to be broken so is insoluble

29
Q

Solubility of polar covalent substances and polar solvents

A
  • they may dissolve as the molecules can attract eachother
  • depends on the dipole strength
  • some molecules are polar&non-polar
  • some molecules are hydrophobic&hydrophillic
30
Q

Simple molecular electrical conductivity

A
  • no mobile charged particles

- so there is nothing to complete an electrical circuit

31
Q

Why is ice less dense than water?

A
  • The H bonds hold H20 molecules apart in an open lattice structure
  • so the solid ice is less dense than liquid water and floats
32
Q

Why does water have a high MP&BP?

A

It has London&H bonds

  • a lot of energy is needed to overcome the H bonds
  • when ice lattice breaks, the arrangement of rigid H bonds is broken
  • when water boils, H bonds break completely
33
Q

What other anomalous properties does water have?

A

-high viscosity and surface tension

34
Q

What is metallic bonding?

A

The attraction of positive ions to delocalised electrons

35
Q

What 3 things are needed for H bonding?

A
  • small H atoms
  • large dipole
  • lone pair of electrons on EN atom so + H CAN LINE UP as it can get very close bc its small

Chemistry AS (6 decks)

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