Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CLS3003-B: Chemistry (Semester 1) > L7 - Chemical Bonding (1) > Flashcards

L7 - Chemical Bonding (1) Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

What is a chemical bond?

A

An attractive force that holds two or more atoms together in a molecule.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are valence electrons?

A

Outer shell electrons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is valency?

A

How many electrons an atom can give / take.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why do atoms combine?

A

To gain stability.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do electrons in atoms organise themselves?

A

Electrons in atoms distribute themselves in orbitals in the most stable / lowest energy configuration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does rearranging electrons between atoms allow?

A

Rearranging electrons between atoms allows the combined molecule to achieve even lower energy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

State the Octet Rule.

A

“Atoms tend to adjust their valence shells to 8e- by losing, gaining or sharing electrons in an attempt to gain a Noble Gas configuration.”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is significant about shells above n=3?

A

Atoms have the option of making more bonds than typically predicted.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe Expanding the Octet.

A

When some atoms hold more than 8 valence electrons in an attempt to obtain stable electronic configuration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The Octet Rule only applies to main group elements. Explain some exceptions.

A

Transition metals using d-orbitals obey the 18-electron rule instead.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe forces between atoms.

A
  • Attractive / repulsive forces operate between 2 atoms when they come close to each other
  • Like charges repel: electron-electron and nucleus-nucleus
  • Opposite charges attract: electron-nucleus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the strength of attraction between atoms.

A
  • Attraction is strong over a short distance, then strength rapidly decreases
  • Negative energy value in order to stabilise interaction (until minimum = optimum bond length)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe what is meant by removing an electron to infinity.

A

When an electron is moved so far from the atom that it is no longer attracted to the nucleus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

State Coulomb’s Law.

A

“Like charges repel and opposite charges attract, with a force proportional to the product of the charges, and inversely proportional to the square of the distance between them.”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Define Electronegativity.

A

The ability of an atom to attract electrons towards itself in a chemical bond.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does electronegativity depend on?

A
  • Number of protons in the nucleus
  • Distance from the nucleus
  • Size of the atom
  • Amount of shielding by inner electrons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does shielding refer to?

A

The number of full shells between the valence shell and the nucleus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the Valence Shell?

A

The outer shell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is used to measure the electronegativity of elements?

A

The Pauling Scale

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the most electronegative element, and what are its properties?

A
  • Fluorine
  • Small atomic radius
  • High nuclear charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Name some highly electronegative elements.

A
  • Nitrogen
  • Oxygen
  • Fluorine
  • Chlorine
  • Krypton
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Name some intermediate electronegative elements.

A
  • Hydrogen
  • Carbon
  • Sulfur
  • Selenium
23
Q

What can electronegativity values and the difference between them be used to predict?

A

Electronegativity values and the difference between them can be used to predict the type of bond which is formed in a particular compound.

24
Q

Describe the different bonds formed by different elements, with reference to electronegativity.

A
  • Left hand side = low values of electronegativity = bonds with same / similar elements, metallic bonds
  • Right hand side = high values of electronegativity = non-metallic compounds when bonding with similar elements, covalent bonds
25
Q

What does a large difference in electronegativity lead to?

A

Complete transfer of electrons = Ionic bonding

26
Q

What does electronegativity predict in different types of bonding?

A
  • Covalent bonding: Electronegativity predicts polarity of bonds and the direction of polarity
  • Ionic bonding: Electronegativity predicts direction of initial transfer of electrons
27
Q

When are ionic bonds formed?

A

When one or more electrons are fully transferred between atoms.

28
Q

What does ionic bonding take place between?

A

Mets and non-metals.

29
Q

Describe the transfer of electrons with reference to the type of atom.

A
  • Metal atoms try to attain noble gas structure by losing electrons to form positive ions (cations)
  • Non-metal atoms try to attain noble gas structure by gaining electrons to form negative ions (anions)
30
Q

What is electrostatic attraction?

A

When positive and negative ions attract each other to give an ionic bond.

31
Q

What does formation of an ionic bond involve?

A

A decrease in energy compared to the two isolated atoms.

32
Q

What is the charge of an ion equal to?

A

The valency of an ion.

33
Q

What is an ionic bond?

A

An electrostatic attraction between positively and negatively charged ions.

34
Q

Describe the properties of ionic bonds.

A
  • Non-directional (the strength of interaction between two ions depends on the distance, but not on the direction)
  • Ionic bonds break when ionic compounds dissolve and dissociate in polar solvents
  • Ionic bonds also break when the substance is melted
35
Q

Describe the features of ionic compounds.

A
  • Formed between metals and non-metals
  • Dissolve / dissociate easily in water and other polar solvents (separated ions are solvated)
  • Conduct electricity when molten and in solution
  • Form crystalline solids with high melting temperatures
36
Q

Describe an Ionic Lattice.

A
  • Every ion is attracted to all other ions with the opposite charge
  • Results in a repeating 3D pattern of anions and cations in the solid state
  • Giant structure
37
Q

Define Lattice Energy.

A

The enthalpy of formation (energy change) of forming one mole of the ionic solid from its gaseous ions.

38
Q

What does lattice energy measure?

A

Bond strength

39
Q

What favours easy cation formation?

A
  • Low ionisation energy of the metal
40
Q

What favours easy anion formation?

A
  • High electron affinity / electronegativity of the non-metal
  • Small size of the non-metal
  • Low charge on anion
41
Q

Describe the factors favouring ionic bonding.

A
  • Large difference in electronegativity between the combining atoms
  • High lattice energy of the ionic compound
42
Q

Describe changes in the atom once ions are formed.

A
  • Positive Ions: Loss of electrons = atomic radius becomes smaller as + charge increases
  • Negative Ions: Gain of electrons = atomic radius becomes larger as - charge decreases
43
Q

Define Polarisation.

A

Distortion of the electron cloud of an atom.

44
Q

Describe polarisation with reference to the size of ions.

A
  • The smaller an ion, the higher its charge, the more polarising power it has (ability to distort the electron cloud of another atom).
  • The larger an atom and the larger its number of electrons, the higher its polarisability.
45
Q

Describe polarisation with reference to anions and cations.

A

Cations are typically smaller than anions and thus, cations tend to have more polarising power while anions tend to be more polarisable.

46
Q

Describe polarisation with reference to the size of charges.

A
  • Small charge / positive charge = generally not highly polarised = strong attraction for electron, so high charge density = ionic bonds (Cations tend to be polarising)
  • Large charge / negative charge = easily polarised = some covalent character in bonds (Anions get polarised)
47
Q

Describe the process of polarisation.

A
  • Negative ion is distorted = has some covalent character
  • Electron density is starting to be pulled from the negative ion to the positive ion so bonding is starting to become directional
48
Q

What is an ideal ionic bond / compound?

A
  • Ionic bond with no polarisation

- Ionic compound which is composed of completely separate, spherical ions

49
Q

What does polarisation result in?

A
  • Non-spherical ions

- Covalent character in the bond

50
Q

When is an ionic compound likely to have some covalent character?

A
  • Cation is small and/or has a high charge = highly polarising
  • Anion is large and/or has a high charge = highly polarisable
51
Q

State Fajan’s Rules.

A

Pure ionic compound:

  • Low positive charge
  • Large cation
  • Small anion

Ionic compound with covalent character:

  • High positive charge
  • Small cation
  • Large anion
52
Q

State the formulae of the following polyatomic ions:

  • Ammonium
  • Cyanide
  • Hydroxide
  • Peroxide
  • Acetate
  • Oxalate
  • Nitrate
  • Sulfate
  • Carbonate
  • Phosphate
  • Permanganate
  • Dichromate
A
  • Ammonium: NH4+
  • Cyanide: CN-
  • Hydroxide: OH-
  • Peroxide: O2 2-
  • Acetate: CH3 CO2 -
  • Oxalate: C2 O4 2-
  • Nitrate: NO3 -
  • Sulfate: SO4 2-
  • Carbonate: CO3 2-
  • Phosphate: PO4 3-
  • Permanganate: MnO4 -
  • Dichromate: Cr2O7 2-
53
Q

State the important anions and cations in the body.

A

Anions:

  • Cl-
  • HCO3 -
  • HPO4 2-
  • SO4 2-
  • PO4 3-

Cations:

  • Na+
  • K+
  • Ca 2+
  • H+
  • Mg 2+
54
Q

What type of bonding is present between polyatomic ions?

A

Covalent

CLS3003-B: Chemistry (Semester 1) (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions