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CHEMISTRY YR12 > bonding > Flashcards

bonding Flashcards

1
Q

Metallic Structure and Bonding definition

A

Metallic bonding is the strong electrostatic attraction of positive metal ions surrounded by a sea of delocalised electrons.

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2
Q

Hint!
When drawing metallic bonding diagrams:

A
  • Always draw at least 6 ions (2 rows of 3)
  • Work out the charge of the ion (i.e. how many electrons are lost from the atom?)
  • Draw the correct number of delocalised electrons. (i.e. the sum of all the charges)
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3
Q

Conductivity

A

All metals are good electrical and thermal conductors. They are good conductors of heat because the delocalised electrons help transfer energy through the metal very efficiently. The delocalised electrons can also flow and hence metals can also conduct electricity very well.

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4
Q

Strength of the metal

A

The majority of metals are very strong as there is a strong electrostatic attraction between the positive metal ions and delocalised electrons.

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5
Q

Malleable and Ductile

A

Metals can be hammered into shape (are malleable) and can be pulled into wires (are ductile) because layers of metal ions can slide past one another

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6
Q

Melting and Boiling Points

A

This is directly linked to the strength of the metallic bonds. The stronger they are, the higher the melting point and boiling point will be.

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7
Q

Structure of metal ion :

A

Giant Lattice (Regular arrangement of particles)

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8
Q

Bonding of metal ion:

A

Strong Metallic Bonds

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9
Q

Structure of covelant :

A

Macromolecular or Simple molecular

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10
Q

Bonding of covelant :

A

Strong Covalent

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11
Q

Definition of covalent :

A

A covalent bond is a shared pair of electrons between two atoms.

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12
Q

How does sharing electrons hold atoms together?

A

The attraction forces are stronger than the repulsion forces and therefore the atoms are held together.

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13
Q

There are three macromolecular structures:

A

Carbon

Silicon

Silicon Oxide

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14
Q

two good examples of macromolecular crystal and why

A

Diamond and graphite

They are both made entirely of carbon, and so are known as allotropes as they are different structural forms of the same element

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15
Q

Diamond

A

consists of carbon atoms each forming 4 covalent bonds to neighbouring atoms.
The arrangement of the bonding is tetrahedral.
This gives diamond a very strong 3D structure.
As a result it is an extremely hard material, it has a very high melting point (over 3700K) and doesn’t conduct electricity as there are no free electrons to carry a flow of charge.

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16
Q

Graphite

A

consists of layers of carbon atoms each forming 3 covalent bonds.
Each carbon has a fourth valence electron however this isn’t used to form a covalent bond but is delocalised between layers.
This means separate layers are held together by Van der Waals forces and this leads to many of graphite’s unusual properties.
It is fairly soft as each layer can slide over the next with just a little force.
It also conducts electricity due to the delocalised electrons. Graphite still has a high melting point though as lots of covalent bonds still need to be broken in order to convert it to a liquid.

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17
Q

Simple Molecular Structures

A

All simple molecular structures are made up of molecules

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18
Q

Ionic Structure and Bonding

A

Structure: Giant Lattice

Bonding: Strong Ionic

19
Q

Ionic Structure and Bonding definition

A

An ionic bond is the strong electrostatic attraction between oppositely charged ions.

20
Q

Electrons are always transferred from…
The metal will therefore always form…

A

…the metal to the non-metal
…a positive ion, and the non-metal will form a negative ion

21
Q

Physical properties of ionic compounds

A

(1) High melting point and boiling point

(2) Electrical conductivity

22
Q

Structural properties

A

Ionic compounds tend to be brittle and shatter easily

23
Q

Total positive charge from positive ions =

A

total negative charge from negative ions

24
Q

Although ionic compounds are made up of charged ions, their overall charge is

A

zero

25
Q

+1

A

Ammonium, NH4

26
Q

-1

A

hydroxide, OH-
nitrate, NO^3-
nitrite, NO^2-
hydrogencarbonate, HCO3-
Chlorate(I), ClO-
Chlorate(V), ClO3-

27
Q

-2

A

carbonate, CO3^2-
sulfate, SO4^2-
sulfite, SO3^2-
dichromate, Cr2O7^2-

28
Q

-3

A

phosphate, PO4^3-

29
Q

Coordinate Bonds Definition
(2 marks):

A

A coordinate bond is a shared electron pair which have both come from the same atom

30
Q

Coordinate bonds are always represented by…

A

an arrow —>

31
Q

The direction of the arrow is important as

A

it points from the atom which donates the pair of electrons to the atom which accepts the pair of electrons.

32
Q

Valence means

A

the outer shell of electrons – the electrons used in bonding

33
Q

Bonding pairs and lone (non-bonding) pairs of electrons are

A

charged clouds that repel each other.

34
Q

To minimise their repulsion the electron pairs

A

repel each other as far apart as possible

35
Q

Strength of repulsion:

A

Lone pair to lone pair > lone pair to bond pair > bond pair to bond pair

36
Q

The strength of the repulsions determines

A

the bond angles between the bond to bond pairs.

37
Q

How to work out the shape and bond angle of a molecule

The shape of a PF5 molecule

A

Step 1 – Determine which element is at the centre of the molecule

This is always the element which there is only one atom of, so Phosphorus is in the middle.

Step 2 – Determine how many valence electrons this atom has

This is the number of electrons on the outer shall, which is the same as the group number. Phosphorus is in group 5 so has 5 valence electrons.

Step 3 – Add 1 for every covalent bond the central atom forms

In PF5 the central P atom is bonding to 5 Fluorine atoms, so is forming 5 covalent bonds. Therefore 5 + 5 = 10

Step 4 – Add 1 for every – charge or take one for every + charge if you have an ion.

PF5 has no overall charge as it is not an ion. Therefore nothing is added to taken leaving 10

Step 5 – Divide the total value by 2 to determine the number of electron pairs.

10 ÷ 2 = 5. Therefore there are 5 electron pairs around P in PF5.

Step 6 – Determine how many electron pairs are bonding, and how many are lone pairs.

PF5 has 5 electron pairs, and has 5 bonds. Therefore all the electron pairs must be bonding pairs and there are no lone pairs.

Step 7 – Select the appropriate 3D shape for the molecule..

Of all the 3D shapes already listed above, only one applies to a molecule with 5 bonding pairs and no lone pairs. This must be diagram (d) which is TRIGONAL BIPYRAMIDAL.

38
Q

Electronegativity Definition
(2 marks):

A

Electronegativity is the power of an atom to attract the pair of electrons in a covalent bond

39
Q

Electronegativity Definition
(2 marks):

A

Electronegativity is the power of an atom to attract the pair of electrons in a covalent bond

40
Q

The factors which determine how electronegative an element are

A
  • The nuclear charge (i.e. the number of protons in the nucleus)
  • The atomic radius (i.e. the distance between the nucleus and outer shell)
  • The shielding (i.e. the number of electrons between the nucleus and the outer shell)
41
Q

As a rule of thumb

A

the closer an element is to Fluorine the more electronegative it is.

42
Q

As a rule of thumb

A

the closer an element is to Fluorine the more electronegative it is.

43
Q

The elements which are highly electronegative have a

A

relatively high nuclear charge, with a relatively low atomic radius and low amount of shielding.

CHEMISTRY YR12 (8 decks)

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