Brainscape's Knowledge GenomeTM

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


See full index

Chemistry Dr L > Electrons, bonding and structure > Flashcards

Electrons, bonding and structure 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 an intermolecular force?

A

An attractive force between neighbouring molecules

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

Why do London forces occur?

A

Due to constant random movements of the electrons within the shells of the atoms in molecules

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

What are the main types of intermolecular forces?

A

•Hydrogen bonding

  • Induced dipole-dipole interactions (London forces)
  • Permanent dipole-dipole interactions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are London forces?

A

They are forces causes by the constant random movement of electrons in atoms’ shells. This movement unbalances the distribution of charge within the electron shells. There is an instantaneous dipole across the molecule which induces a dipole in neighbouring molecules which then do the same. The small induced dipoles attract one another cause weak intermolecular forces( London forces)

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

What factors affect London forces?

A

The size of London forces increase with increasing number of electrons. The greater the number of electrons the larger the induced dipoles and the greater the attractive forces between molecules

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

What is the effect of London forces on boiling points?

A

As the London forces are so weak non-polar molecules which only have London forces have very low boiling points.

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

What is a hydrogen bond?

A

A strong permanent dipole-permanent dipole attraction between an electron-deficient hydrogen atom on one molecule and a long pair of electrons on a highly electronegative atom (O,N or F) on a different molecule.

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

Why is ice less dense than water?

A

When ice forms, water molecules arrange themselves into an orderly pattern and hydrogen bonds form between the molecules. Ice has an open lattice with hydrogen bonds holding the water molecules apart

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

Why does water have a higher than expected boiling point?

A

The hydrogen bonds are much stronger than other intermolecular forces which require extra strength to overcome the forces to boil water

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

What are dative bonds?

A

A shared pair of electrons that have been provides by only one of the bonding atoms- also known as a co-ordinate bond

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

Giant metallic lattice:

A

~bonding present is metallic bonding
~have a high melting and boiling point because of the strong attraction between the positive metal ions and the delocalised electrons
~don’t dissolve because of the strength of the attraction between the metal ions and the electrons
~conduct electricity because the electrons are free to move and carry charge
~the delocalised electrons move around and the metal ions are attracted to them keeping the structure in place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does the strength of metallic bonding depend on?

A

~the charge of the metal ions
~the size of metal ions (the smaller the metal ion the closer the delocalised electrons are from the nucleus so there is a greater attraction between them meaning a greater metallic bond)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a covalent bond?

A

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

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

Giant covalent structures:

A

~the lattice is defined as a giant regular lattice
~have high melting and boiling points because there is a lot of strong covalent bonds within the lattice
~don’t conduct electricity because there are no free electrons or ions apart from graphite
~don’t dissolve because the covalent bonds in the lattice are too strong to be broken by either polar or non-polar solvents

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

Simple molecular structures:

A

~formed between 2 non-metals
~are covalently bonded substances that contain only a few atoms held together by covalent bonds
~have low melting and boiling points because the intermolecular forces between simple molecules are weak
~don’t conduct electricity as they have no free electrons or ions to Cary a charge
~dissolve in non-polar solvents due to weak bonds
~a lattice is a series of points that are arranged in a distinct pattern
~atoms of each molecule are held together by strong covalent bonds
~different molecules are held together by weak intermolecular forces

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

Giant ionic lattices:

A

~formed from metals and non-metals. All ionic compounds exist as giant ionic lattices when solid
~each ion is surrounded by oppositely charged ions which attract each other from all directions forming a 3D giant ionic lattice
~have high melting and boiling points because of strong electrostatic forces
~don’t conduct electricity when solid as ions are held firmly in place so they can’t move to carry a charge
~dissolve in polar substances e.g. water as they can break down the lattice by surrounding each ion to form a solution. The slight charges with the polar substance are able to attract the charged ions in the giant ionic lattice so the lattice is disrupted and ions are pulled out of it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are molecular ions?

A

Groups of covalently bonded atoms with a charge

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

What are properties of ionic compounds?

A

~Can’t conduct electricity (ions in a fixed place so can’t carry a charge when solid)
~Dissolved in polar solvents e.g. water (polar water molecules break down the ionic lattice and surround each ion forming a solution)
~High melting and boiling points (strong electrostatic forces between the ions)

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

What is the Octet rule?

A

The tendency for an atom to acquire a noble gas configuration

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

What happens to covalent bonds if the atoms are different?

A

One of the atoms is likely to attract the bonding electrons more. The bonding atom with a greater attraction for the electrons pair is said to be more electron negative than the other atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is a permanent dipole?

A

A small charge difference across a bond that results from a difference in the electronegative of the bonded atoms.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is electronegativity?

A

It measures the attraction of a bonded atom for the pair of electrons in a covalent bond. It increases towards the top right of the periodic table with fluorine having the most electronegative atoms.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What determines the shape of a molecule or ion?

A

The number of electron pairs in the outer shell surrounding the central atoms as electrons have a negative charge, each electron pair repels other electron pairs. The shape adopted will be the shape that allows all the pairs of electrons to be as far apart as possible.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is a modified version of the Octet Rule?

A

~Unpaired electrons pair up

~The maximum number of electrons that can pair up is equivalent to the number of electrons in the outer shell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How many covalent bonds can atoms of non-metals in group 17 form?

A

1, 3, 5 or 7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How many covalent bonds can atoms of non-metals in group 16 form?

A

2, 4 or 6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How many covalent bonds can atoms of non-metals in group 15?

A

3 or 5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the expansion of the Octet?

A

~When the Octet rule is broken and atoms end up with more than 8 electrons in its outer shell
~Atoms of non-metals in group 15 can form 5 covalent bonds depending on how many electrons are used in bonding
~Atoms of non-metals in group 16 can form 2,4 or 6 covalent bonds depending on how many electrons are used in bonding
~Atoms of non-metals in group 17 can for 1, 3, 5 or 7 covalent bonds, depending on how many electrons are used in bonding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the average bond enthalpy?

A

A measure of the average energy of a bond the energy needed to break it as not all covalent bonds are the same strength some are much stronger than others

30
Q

What is a multiple bond?

A

Some non-metallic atoms can share more than one pair of electrons with another atom

31
Q

What is a lone pair?

A

A pair of electrons that are not used for bonding. It gives a concentrated region of negative charge around the atom. They can influence the chemistry of a molecule

32
Q

What is covalent bonding?

A

It occurs in compounds consisting of 2 non-metals. Element are shared between the atoms and are attracted to the nuclei of both bonded atoms. This attraction overcomes the repulsion between the 2 positively charged nuclei. Covalent bonds act in one direction only (atoms involved in the bond)

33
Q

What is metallic bonding?

A

It occurs in metals. Electrons are shared between all the atoms. The metal is held together by the attractions between all the positive ions and all the negative electrons

34
Q

What is a single bond?

A

If atoms are bonded by one shared pair of electrons

35
Q

What is ionic bonding?

A

Ionic bonding occurs in compounds consisting of a metal and a non-metals. Electrons are transferred from the metal atom to the non-metal atom forming oppositely charged ions that attract each other

36
Q

Why do elements react and bond together?

A

As in chemical reactions electrons transfer and elements involved in chemical reactions will often become more stable by combining with other elements or transferring electrons. Elements react in ways that allow them to end up with the electron configuration of a noble gas

37
Q

What shape does a p-orbital have?

A

3D dumbbell shape

38
Q

What shape does a s-orbital have?

A

Spherical shape

39
Q

What is an orbitals?

A

A region around the nucleus that can hold up to 2 electrons with opposite spins

40
Q

What is ionic bonding?

A

Electrostatic bond between 2 oppositely charged ions

41
Q

What is a ionic bond?

A

An electrostatic bond between 2 oppositely charged ions

42
Q

Why does sodium chloride have a lattice structure?

A

Each ion is electrostatically attracted in all directions to ions of the opposite charge so it forms a lattice

43
Q

What does mean ‘expand the octet’ mean?

A

When a compound uses d-orbitals to have more than 8 electrons in their outer shell

44
Q

What is an example of a compound with dative bonding?

A

An ammonium ion (NH4+)

45
Q

Why are there greater angles between lone pairs?

A

Because repel as much as they can as they are all negatively charged so they repel more than bonding pairs

46
Q

What is the bond angle of a compound with no lone pairs?

A

109.5

47
Q

What is the bond angle of a compound with 1 lone pair?

A

107

48
Q

What is the bond angle of a compound with 2 lone pairs?

A

104.5

49
Q

What is the bond angle of a linear molecule?

A

180

50
Q

What is the bond angle of a trigonal planar?

A

120

51
Q

What is the bond angle in a tetrahedral?

A

109.5

52
Q

How many lone pairs is in a tetrahedral shape?

A

None

53
Q

What is the bond angle in a trigonal pyramidal?

A

107

54
Q

How many lone pairs are in a trigonal pyramidal?

A

One

55
Q

What is the bond angle in a non linear compound?

A

104.5

56
Q

What is the bond angle in a trigonal bipyramidal?

A

90 and 120

57
Q

What is the bond angle in a octahedral?

A

90

58
Q

How do you work out the number of electron pairs in a covalent compound?

A
  1. ) First work out how many electrons there are around the central atom
  2. ) Write down the number of electrons in the outer shell of the central atom (the group no. in the periodic table, but for noble gases it is 8)
  3. ) Add one electron for each bond being formed (from other atoms)
  4. ) Allow for any ion charge
  5. ) work out how many bonding pairs and lone pairs of electrons there are
  6. ) Divide by 2 to find the total number of electron pairs around the central atom
  7. ) Work out how many of these are bonding pairs, and how many are lone pairs- you know how many bonding pairs there are as you know how many atoms are joined to the central atom (if only single bonds for)
  8. ) Use this information to find the shape
59
Q

What is electronegativity?

A

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

60
Q

What is electronegativity measure in?

A

The Pauling Scale- the greater the value the greater the electronegativity

61
Q

What is the trend for electronegativity?

A

It increases across periods , decreases down groups (ignoring the Noble gases)

62
Q

What happens in covalent bond between atoms with different electronegativities?

A

The bonding electrons are pulled towards the more electronegative atom making the bond polar. This causes a permanent dipole

63
Q

What is a permanent dipole?

A

The difference in charge between 2 atoms causes by a shift in electron density

64
Q

What happens if polar bonds are symmetric?

A

The dipoles cancel out so the molecule is non-polar

65
Q

How can electronegativity be used to predict what type of bonding occurs between 2 atoms?

A

The higher the difference in electronegativity the more ionic in character the bonding becomes

66
Q

What are induced dipole-dipole interactions (London forces)?

A
  • Electrons move very quickly, at any moment the electrons in an atom are likely to be more one side than the other making that side slightly negative. This causes the atom to have a temporary dipole.
  • The dipole causes another temporary (induced dipole) on the opposite side of a neighbouring atom. The dipoles are attracted to each other.
  • The electron constantly move, so the dipoles are constantly being created and destroyed
67
Q

What factors affect the strength of London forces?

A
  • more electrons=stronger London forces=higher boiling points
  • greater surface area= bigger exposed electron cloud=stronger London forces=higher boiling points
68
Q

What is a permanent dipole-dipole interaction?

A
  • The slightly negative and slightly positive charges on polar molecules cause weak electrostatic forces of attraction between molecules
  • This happens in addition of London forces
69
Q

What is hydrogen bonding?

A

Strong intermolecular force when hydrogen covalently bonds with oxygen, nitrogen or fluorine (very electronegative atoms)

70
Q

What is ice less dense than water?

A
  • Ice is held in a lattice by hydrogen bonds
  • When it melts they break so ice has more hydrogen bonds than liquid water
  • Hydrogen bonds are long so ice is less dense
71
Q

When you melt/boil a simple covalent compound what bonds are being broken?

A

The intermolecular forces that hold the molecules together

Chemistry Dr L (3 decks)

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