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AS Chemisrty > C7 Bonding and structure > Flashcards

C7 Bonding and structure Flashcards

1
Q

Ionic bond

A

The electrostatic attraction between oppositely charged ions, the attraction between positive and negative ions

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2
Q

Cations

A

Positively charged ions

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3
Q

Anions

A

Negatively charged ions

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4
Q

Covalent bond

A

A single covalent bond is formed by the sharing of two electrons between two adjacent atoms. Each atom provides one electron.
The electrostatic attraction between the shared pair of electrons and the nuclei of the two bonded atoms constitutes the covalent bond

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5
Q

Dative covalent bond

A

A bond in which two atoms share two electrons but one atom provides more electrons. The electrostatic attraction between the shared pair of electrons and the nuclei of the two bonded atoms constitutes the covalent bond.

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6
Q

Electron pair repulsion

A

States that the electron pairs repel each other and the overall shape of the molecule depends on the number and type of electron pairs around the central atom. Lone pairs (non-bonded pairs) repel more than bonded pairs of electrons.

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7
Q

Delocalised

A

Electrons are bonding electrons that are not fixed between two atoms in a bond. They are mobile and are shared by several or many atoms

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8
Q

Metallic

A

Is the electrostatic attraction between the delocalised electrons and the positive ions held within the lattice

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9
Q

Electronegativity

A

The ability of an atom of an element to attract the shared pair of electrons in a covalent bond

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10
Q

Intermolecular forces

A

Are forces of attraction that occur between molecules

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11
Q

Permanent dipole-dipole interactions

A

The weak electrostatic attractions between polar molecules that are essentially covalent but have some ionic character

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12
Q

Hydrogen bonds

A

The relatively strong electrostatic attractions between polar molecules that contain hydrogen covalently bonded to elements with high electronegativity such a fluorine, oxygen and nitrogen

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13
Q

Induced dipole-dipole interaction

A

3 key features:
• the movement of electrons
• the instantaneous dipole induces other dipoles in neighbouring atoms/molecules
• Two dipoles generate a weak temporary force of attraction between the atoms/molecules

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14
Q

Types of bonding

A

Ionic- losing or gaining electrons

Covalent- sharing electrons

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15
Q

Isoelectronic

A

The same number of electrons

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16
Q

Ionic bonds

A

Metal and non metal
Losing electron= positive ion
Gaining electron= negative ion

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17
Q

Dot and cross diagrams

A

Simplified structures showing the electrons in rings around the nucleus

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18
Q

Covalent bonds

A

Two non metals

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19
Q

Single covalent bonds

A

Formed through the sharing of two electrons by adjacent atoms
Eg. H2 or Fl2

20
Q

Double bonds

A

If 2 atoms share 4 electrons, 2 covalent bonds see formed (a double bond)

21
Q

Triple bonds

A

Sharing 6 electrons

22
Q

Lone pairs of electrons

A

Can form a variation on the covalent bond known as a dative bond
Affect the shape of molecules
Are important in the chemical reactions of some compounds including water and ammonia
Can behave as nucleophiles in organic reactions
Non bonding pair of electrons

23
Q

Dative covalent (coordinate) bonding

A

One atom shares 2 electrons to create a bond with another atom. It uses a lone pair of electrons

24
Q

Properties of covalent compounds

A 
Liquids or gases
Low melting points
If solid- not dense, soft, easily broken
Exist as small discrete molecules
Bond within molecules are strong 
Bonds between individual molecules are much weaker and are easily broken
25
Main properties of covalent compounds
Low melting and boiling points Poor conductor of electricity Solvable in non polar solvents such as hexane
26
Electron repulsion theory
The shape of a molecule is determined by the numbers of bonded and lone electron pairs around the central atom. A simple model of molecular shape is based on the fact that pairs of electrons repeal each other to be as far apart in space as possible.
27
Order of strength of repulsion
Lone pair-lone pair > lone pair-bonded pair > bonded-bonded pair
28
2 bonded and 0 lone pairs | shape
Linear | 180 degree angle
29
3 bonded and 0 lone pairs | Shape
Trigonometry planar | 120 degree angle
30
4 bonded and 0 lone pairs | Shape
Tetrahedral | 109.5 degree angle
31
5 bonded and 0 lone pairs | Shape
Bipyramidial | 120 and 90 degree angles
32
6 bonded and 0 lone pairs | Shape
Octahedral | 90 degree angle
33
3 bonded pairs and 1 lone pair | Shape
Pyramidal | 107 degree angle
34
2 bonded and 2 lone pairs | Shape
Angular (bent) | 104.5 degree angle
35
Metallic bonding
Metal ions in the lattice and mobile delocalised electrons
36
Properties of metallic compounds
High melting and boiling points Good conductor of electricity Malleable and ductile
37
Many bonds are described as essentially:
Covalent with some ionic character | Ionic with some covalent character
38
Bond polarity
In a covalent molecule, ionic character is introduced when the covalent bond is not shared evenly between the components. This is the result of difference in electronegativity
39
Trends in electronegativity in the periodic table
Electronegativity increases across a period and up a group
40
In a covalent bond an element with greater electronegativity
Attracts the bonding electron towards its self | Elements with higher electronegativity have stronger attraction for the shared electrons
41
Dipole
A covalent bond with some charge separation | Described as essentially covalent
42
Polar bonds and polar molecules
If a molecule is symmetrical, the dipoles cancel out even if the bonds are polar Non symmetrical shapes are always polar
43
Force needed to break ionic/covalent/metallic bonds
200-800 kJ mol^-1
44
Force needed to break intermolecular forces
2-40 kJ mol^-1
45
Uses of hydrogen bonding
Amino acids, peptides, proteins
46
Hydrogen bonding
Special form of permanent dipole-dipole interactions | The presence of a lone pair on the electronegative is essential for hydrogen bonding
47
Giant covalent structures
Carbon covalently bonded in hexagonal rings or in a tetrahedral shape Graphite, graphene, silicon, silicon dioxide and diamond

AS Chemisrty (14 decks)

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