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Advanced Higher Chemistry > Shapes of Molecules and Polyatomic Ions > Flashcards

Shapes of Molecules and Polyatomic Ions Flashcards

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1
Q

How are atoms held together in chemical substances?

A

By chemical bonds

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2
Q

What are dative bonds?

A

Dative bonds form when one atom provides both the electrons that form the covalent bond.

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3
Q

What is the name of shape of an atom with 180 degree bond angles?

A

Linear

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4
Q

What is the name of the shape of molecule with three atoms attached to the central atom and the bond angle?

A

Trigonal Planar with 120 degree bond angle

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5
Q

What is the name of the shape of molecule with two atoms attached to the central atom and 1 lone pair of electrons and the bond angle?

A

Angular with <120 degree bond angle

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6
Q

What is the name of the shape of molecule with four atoms attached to the central atom and the bond angle?

A

Tetrahedral with 109.5 bond angle

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7
Q

What is the name of the shape of molecule with three atoms attached to the central atom with one lone pair of electrons?

A

Trigonal pyramidal with <109.5 bond angle

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8
Q

What is the name of the molecule with two atoms attached to the central atom with two lone pairs of electrons?

A

Bent/angular with «109.5 bond angle

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9
Q

What is the name of the molecule with five atoms attached to the central atom and the bond angle?

A

Trigonal Bipyramidal with bond angles of 90 and 120 degrees.

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10
Q

What is the name of the molecules with four atoms attached to the central atom with one pair of lone electrons?

A

Sawhorse/Seesaw with bond angle of <120 and <90 degrees

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11
Q

What is the name of the molecules with three atoms attached to the central atom with two lone pairs of electrons?

A

T-shape with bond angle <90 degrees

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12
Q

What is the name of molecules with two atoms attached to the central atom with three lone pairs of electrons?

A

Linear with bond angle of 180 degrees.

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13
Q

What is the name of the molecule with six atoms attached to the central atom?

A

Octahedral with 90 degree bond angle

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14
Q

What is the name of the molecule with 5 atoms attached to central atom with one lone pair of electrons?

A

Square pyramidal with <90 bond angle

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15
Q

What is the name of the molecule with 4 atoms attached to central atom with two lone pairs of electrons?

A

Square planar with 90 degree bond angles

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16
Q

What is the name of the molecule with 3 atoms attached to the central atom with three lone pairs of electrons?

A

T-shape with bond angle <90

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17
Q

What is the name of the molecule with two atoms attached to the central atom with four lone pairs of electrons?

A

Linear with bond angle of 180 degrees.

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18
Q

What is the name, symbol and charge of the chloride ligand?

A

Chloride, Cl^-1 (-1)

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19
Q

What is the name, symbol and charge of the oxide ligand?

A

Oxido, O^-2 (-2)

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20
Q

What is the name, symbol and charge of the cyanide ligand?

A

Cyanido, CN^-1 (-1)

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21
Q

What is the name, symbol and charge of the hydroxide ligand?

A

Hydroxido, OH^-1 (-1)

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22
Q

What is the name, symbol and charge of the oxalate ligand?

A

Oxalato, O4C2^-2 (-2)

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23
Q

What is the name, symbol and charge of the ammonia ligand?

A

Ammine NH3 (0)

24
Q

What is the name, symbol and charge of the water ligand?

A

Aqua, OH2 (0)

25
Q

What is the name, symbol and charge of the carbon monoxide ligand?

A

Carbonyl, CO (0)

26
Q

When is the complex the most stable?

A

D

27
Q

When is r on the diagram?

A

The distance between the two nuclei (bond length)

28
Q

What is the repulsive effect?

A

When electron pairs are pushed as far apart as possible as possible minimising repulsion between them.

29
Q

What is the trend of the repulsive effect?

A

bonded:bonded < bonded:lone < lone:lone

30
Q

What do we call the repulsive effect?

A

Valence Shell Electron Pair Repulsion (VSEPR)

31
Q

How do you calculate the number of electron pairs?

A

-taking the total number of valence (outer) electrons on the central atom and adding
one for each atom attached
- adding an electron for every negative charge
- removing an electron for every positive charge
-dividing the total number of electrons by two to give the number of electron pairs

32
Q

What are transition metals?

A

d-block transition metals are defined as metals with an incomplete d subshell in at least on of their ions.

33
Q

What are the exceptions to transition metals and why?

A

Zinc - completed d orbitals
Scandium - unfilled d orbitals

34
Q

What are oxidation states?

A

Similar to valency that an element has when it is part of a compound.

35
Q

What are the rules for assigning oxidation numbers?

A
  • uncombined elements have an oxidation number of 0
  • ions containing single atoms have an oxidation number that is the same as the charge
    on the ion
  • in most of its compounds, oxygen has an oxidation number of −2
  • in most of its compounds, hydrogen has an oxidation number of +1
  • the sum of all the oxidation numbers of all the atoms in a neutral compound must add
    up to zero
  • the sum of all the oxidation numbers of all the atoms in a polyatomic ion must be equal
    to the charge on the ion
36
Q

What can oxidation numbers be used to determine?

A

Whether an oxidation-reduction reaction has taken place. Increased oxidation number means oxidation has taken place where as a decrease means that reduction has taken place.

37
Q

What does it usually mean if a compound has a high oxidation state?

A

May be an oxidising agent

38
Q

What does it usually mean if a compound has a low oxidation state?

A

May be a reducing agent

39
Q

What does it mean if there has been a distinct colour change?

A

Ions have changed from one oxidation state to another.

40
Q

What is a complex?

A

Consists of a central metal ion surrounded by ligands.

41
Q

What are ligands?

A

Ligands are negative ions or uncharged molecules with one or more non-bonding pairs of electrons. They are electron donors, giving their non-bonding electrons to unfilled metal orbitals. This forms dative covalent bonds.

42
Q

What are monodentate ligands?

A

Monodentate ligands will donate one pair of electrons to the central transition metal forming a dative covalent bond. examples include chloride, cyanide, ammonia and water.

43
Q

What are bidentate ligands?

A

Bidentate ligands will donate two electron pairs. These electron pairs must be on separate atoms in order to orientate around a central transition metal. examples include oxalate ion and 1,2-diaminoethane

44
Q

What is the coordination number?

A

The total number of bonds from the central metal ion to the ligand(s).

45
Q

Why are certain transition metals coloured?

A

They absorb light in certain parts of the visible spectrum.

46
Q

What is the colour that is seen?

A

It is the complementary colour that to that absorbed.

47
Q

What happen if white light is seen?

A

All the colours are absorbed

48
Q

What happens to the colour of transition metals when ligands are attached?

A

When different ligands are attached to the transition metal, the energy absorbed will change. This results in different wavelengths of light being transmitted and accounts for a change in the colour of transition metal compounds.

49
Q

Why are transition metals able to absorb light?

A

Due to the 5 degenerate d-orbitals splitting in terms of energy.

50
Q

Where do ligands attach and what is the effect of this?

A

Ligands attach along the dz^2 and dx^2y^2 which will result in the electrons in the orbitals being repelled by electrons in the ligands. The orbitals will have higher energy than the three d orbitals that lie between the axes and therefore the 5 d orbitals are no longer degenerate.

51
Q

How is colour produced in transition metals?

A

In terms of d-d transitions. Light is absorbed when electrons in a lower energy are promoted to a higher energy level.

52
Q

What do different ligands produce?

A

different crystal field splittings complexes of the same metal ion with different ligands with different colours

53
Q

Why can transition metals be considered as catalysts?

A

The presence of unpaired d-electrons or empty-d orbtials allow intermediate complexed to form, providing alternative reaction pathways of lower activation energy.

54
Q

What is a homogenous catalyst?

A

They are in the same phase as the reactants. These can from intermediate complexes with the reactive molecules which results in a change in oxidation state.

55
Q

What is a heterogenous catalyst?

A

Are in different phase to reactants e.g. liquids and solids. Adsorption of the reaction molecules onto active sites allow the reaction to be catalysed

Advanced Higher Chemistry (14 decks)

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