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Semester One Chemistry > Covalent Bonding > Flashcards

Covalent Bonding Flashcards

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0
Q

Why do non metals bond?

A

Because they both want to complete their outer shell (octet rule) (except hydrogen), to be stable.

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1
Q

What is covalent bonding?

A

Covalent bonding is when two or more non-metal atoms join together by sharing electrons.

Eg: H2O and CO2

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2
Q

What is a covalent bond?

A

A covalent bond is the electrostatic attraction between the negatively charged shared pair of electrons and the positive nucleus of each atom.

The electrostatic attraction holds the atoms together and forms the molecule.

A covalent bond is a bond formed by the sharing of electrons.

Covalent bonds are where two atoms share one or more pairs of valance electrons.

These bonds are the result of the force of attraction between shared electrons and the nuclei of the non-metal atoms in the bond.

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3
Q

What is a molecule?

A

A molecule is a discrete (separate) group of non-metallic atoms held together by covalent bonds.
The atoms are combined in a fixed ratio and are electrically neutral.

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4
Q

What are covalent molecular substances?

A

Covalent molecular substances are substances held together by covalent bonds and include elements and compounds. These substances are made up of molecules.

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5
Q

What are the properties of covalent molecular substances?

A
  • Low melting and boiling points. (Liquids or gases at room temp). Therefore the intermolecular forces of attraction are very weak and little energy is required to break them.
  • Poor conductors of electricity. Do not conduct electricity in the solid or molten states. Therefore no charged particles are free to move through the lattice. Electrically neutral.
  • Soft and easy to scratch.
  • polar or non polar depending on bonds and overall charge
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6
Q

What are bonding electrons?

A

Bonding electrons are the single electrons that are available for sharing, and determine the number of bonds and atom can form with other non-metals.

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7
Q

What are non-bonding electrons or lone pairs?

A

The valance electrons not involved in forming a bond. They are paired electrons that are not available for sharing.

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8
Q

What is the VSEPR theory?

A

A set of rules that we can use to look at a 2D Lewis structure of a molecule and figure out work the molecule would look like in 3D.
Electrons want to be as far away as possible from each other.
We use it to predict the shape of a molecule.

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9
Q

What does VSEPR stand for?

A

Valence Shell Electron Pair Repulsion

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10
Q

Molecular shapes can be determined by using…

A

electron dot diagrams and VSEPR theory, which allows us to determine the best shape for minimum repulsion between the electron pairs around the central atom.

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11
Q

Molecular shapes include:

A 
Linear
V-Shaped/Bent
Trigonal Planar
Trigonal Pyramidal
Tetrahedral
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12
Q

Linear

A

If the central atom has one bonding pair or one pair on either side.
Eg: H2 (single bond), CO2 (double bond)

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13
Q

V-Shaped/Bent

A

If the central atom has two bonding pairs and one or two lone pairs.
Eg:SO2 (one) and H2O (two)

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14
Q

Trigonal Planar

A

If the central atom has three bonding pairs and no lone pairs.
Eg: C2H4

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15
Q

Trigonal Pyramidal

A

If the central atom has three bonding pairs and one lone pair.
Eg: NH3

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17
Q

Tetrahedral

A

If the central atom has four bonding pairs and no lone pairs.
Eg: CH4

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18
Q

What are the properties of non-metals?

A
  • Don’t have a shine
  • Are brittle
  • Cannot be bent to form shapes
  • Are poor conductors of electricity
  • Melt at low temperatures
  • Many are gases at room temperature
  • Attract electrons easily but don’t give them up easily
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19
Q

Electronegativities

A

Non-metallic atoms have high electronegativities, which means that they have a strong attraction for the shared electrons in a covalent bond.
Differing electronegativities cause electrons to be unequally shared, and can affect the polarity of the bond, as can the shape of the molecule.

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19
Q

Molecular substances

A

Do not conduct electricity in the solid or molten states and have low melting and boiling temperatures.

20
Q

As the Electronegativity difference goes up the…

A

Type of intramolecular bonding changes.

21
Q

Non-polar covalent bonds

A

Occur in molecular elements, which share electrons equally as their atoms have the same electronegativity. Linear, trigonal planar, and tetrahedral molecules are non-polar molecules when equal polar bonds cancel each other out.

22
Q

Properties of non polar covalent molecules

A

Symmetrical
No overall charge
Equal sharing of electrons

23
Q

Polar covalent molecules

A

Result when the two atoms in the bond have different electronegativities and the pairs of electrons are shared unequally.
These bonds are called bond dipole. Trigonal pyramidal or v-shape/bent molecules are polar molecules.

Polar substances dissolve in polar solutions.

24
Q

Properties of polar covalent molecules

A

Asymmetrical
Overall charge- Dipole charge (- and +)
Unequal sharing of electrons

25
Q

Intramolecular forces

A

Strong forces of attraction that hold atoms together within molecules.

26
Q

Which is weaker and why?

Inter- or intramolecular forces?

A

Intermolecular forces are weaker than intramolecular forces because they are chemical bonds within a molecule….

27
Q

Intermolecular forces

A

Weak forces of attraction between molecules.

28
Q

What are the intermolecular forces?

A

Dispersion forces
Dipole-dipole forces
Hydrogen bonding

29
Q

Dispersion forces

A

Are found in ALL discrete molecules and increase with the size of the molecule and the corresponding number of electrons.
Weakest intermolecular force.
The strength of dispersion forces depends on the number of electrons and the shape of the molecule.
They occur when the nuclei attract electrons from neighbouring atoms.

29
Q

Dipole-dipole interactions

A

Are only found in polar discrete molecules.

They occur when the positive side of one molecule attracts the negative side of another molecule.

31
Q

Hydrogen bonding

A

Is a special case of dipole-dipole interaction.
It is found only in molecules where a hydrogen atom is directly bonded to a more electronegative fluorine, oxygen, or nitrogen atom.
These bonds are stronger than other dipole-dipole bonds and result in higher melting and boiling points.
Strongest intermolecular force.
Hydrogen bonding occurs between two molecules in which hydrogen is bonded to nitrogen, oxygen or fluorine.

34
Q

What dissolves what?

A

Like dissolves like.

Polar substances dissolve in polar solutions.

35
Q

Steps to naming binary covalent compounds.

A
  1. Write the first elements name out in full.
  2. Write the second element as it’s anions name. (Suffix -ide)
  3. Write the correct Greek prefix in front of each of the elements corresponding to its number. (Don’t put mono of the first element)
36
Q

What are covalent network lattices?

A

Non metals that form giant structures in which no individual molecules exist. The form a three dimensional network lattice called a covalent network lattice.

37
Q

What is a type of network lattice?

A

Diamond

38
Q

What is diamond a network lattice made of?

A

Carbon

39
Q

What type of bonding does diamond have?

A

Carbon atoms bond tetrahedrally with other carbon atoms. 3D

40
Q

What are the properties of diamond?

A 
Shiny
Hard (hardest natural material on earth)
Brittle
Non polar
High melting and boiling points
Used in jewellery, drills, cutting saws
41
Q

What are the properties of covalent network lattices?

A

-Hard
-Difficult to scratch
-High melting and boiling points
Because particles are held quite rigidly together.
-Stronger dispersion forces
-Non-conductors of electricity- no free ions
-Brittle- must be cut in a specific way or they will shatter
-Non polar- chemically inert, insoluble in water

42
Q

What are covalent layer lattices?

A

They are countless atoms held strongly together in planes by covalent bonds. 2D. Held together by weaker dispersion forces.

43
Q

What is a type of layer lattice?

A

Graphite

44
Q

What is graphite?

A

It is an oily black, opaque solid with a metallic sheen.

45
Q

What is graphite a layer lattice of?

A

Carbon

46
Q

What type of bonding does graphite have?

A

Carbon atoms bond in hexagonal rings (6 carbon atoms) in a 2D structure.

47
Q

What are the properties of graphite?

A

Good conductor of electricity- delocalised electrons can move across the layers under an electrical influence.
Flexible, slippery to touch and flaky- weak dispersion forces between the layers allow them to slide over each other.
High melting and boiling point- difficult to break the strong bonds within the layers.
Black, opaque, solid with a metallic sheen- light interacts with delocalised electrons.

48
Q

What are allotropes?

A

Allotropes are one of two or more existing forms of an element.

49
Q

When the state of matter changes…..

A

The intramolecular bonds are unaltered.
The intermolecular bonds are disrupted.
Eg: Ice is solid/frozen water (H2O), when it melts it is liquid water (H2O).

50
Q

What are molecular compounds?

A

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Semester One Chemistry (7 decks)

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