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Unit 1 Chemistry > Covalent Bonding > Flashcards

Covalent Bonding Flashcards

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1
Q

What is the name of a covalent substance

A

Covalent molecular substance

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2
Q

What do covalent bonds create

A

Molecules

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3
Q

What is a covalent molecular element

A

Identical atoms forming a covalent bond

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4
Q

What are discrete molecules

A

When each molecule is separate or distinct of another

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5
Q

What are monatomic and diatomic molecules

A

Monatomic are molecules are made by one atom of a element and are the noble gases

Diatomic are molecules that have two of the same element in a molecule and each having a full valence shell

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6
Q

Do non metals have high or low electronegativity

A

High

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7
Q

What is the atom called with the most covalent bonds

A

The central atom

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8
Q

Explain a double or triple bond

A

When atoms share two or more electrons each

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9
Q

What does the VSEPR theory state

A

That lone pairs in the molecule repel each other and take a position as far away as possible from one another

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10
Q

What is a non polar bond

A

When atoms in a molecule have the same electronegativities they share the electrons equally and are evenly distributed.

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11
Q

What is a polar covalent molecule

A

When one atom within a molecule has a higher electronegativity therefore it pulls the shared electrons closer to its nucleus and therefore has a slight negative charge and the other has a slight positive charge

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12
Q

What is a dipole

A

When in a molecule there is a positive and negative charge separation, that is a polar molecule

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13
Q

What is a molecular dipole or a dipolar molecule

A

When a covalent molecule is polar, one side is positive and the other negative.

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14
Q

What are the rules for determining the polarity of a molecule

A
  1. Draw the proper structural diagram of the molecule
  2. Identify the electronegativity of all atoms
  3. Use the shape to determine if the molecule is polar. If bond dipoles cancel each other out then it is non polar (in opposite directions)
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15
Q

In general what shape molecules are polar and not polar

A

Non-POLAR: linear, planar and tetrahedral

POLAR: v-shaped or Pyramidal

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16
Q

What is the difference between intermolecular force and intramolecular forces

A

Intermolecular: the forces between molecules of a substance

Intramolecular: the forces inside a molecule

17
Q

What does intermolecular forces usually determine

A

Whether the compound exist in solid liquid or gas state

18
Q

From weakest to strongest list the intermolecular forces

A

Dispersion forces
Dipole-dipole interactions
Hydrogen bonding

19
Q

Explain dispersion forces

A

This occurs when the nuclei of atoms in one molecule are able to attract the electrons of neighbouring molecules. All covalent molecules have dispersion forces

20
Q

What determines the strength of a dispersion force

A

The amount of electrons, more = stronger

21
Q

What is an instantaneous dipole

A

Due to the electrons moving so fast around the molecule, at any point in time there is a high chance that most electrons of that molecule are found in one side of the molecule. This can cause a shift in neighbouring molecules and therefore create a weak dipole bond

22
Q

Explain Dipole-dipole interactions

A

This occurs when molecules are polar. The positive side of one molecule is attracted to the negative side of another and vise versa. Thus all the molecules in the sample are being attracted this force. This results in a higher boiling point and is more likely to occur as a solid or liquid in room temp

23
Q

Explain hydrogen bonding

A

When hydrogen bonds to a higher electronegative atom its electon moves closer to said atom leaving hydrogen un shielded. The other molecule can be a lot closer to the hydrogen atom and causes a very strong bond. Each atom has to be bonded with hydrogen

24
Q

What elements can only create hydrogen bonding

A

Fluorine, oxygen, nitrogen

25
Q

What is covalent bonding?

A

Covalent bonds are formed when non metal atoms share their electrons

26
Q

What are some of the properties of molecular substances

A

Do not conduct electricity in solid or molten form - due to the molecules being neutral

If dissolved in water without reacting they will not conduct electricity

Some molecules dissolve in water to produce ions - therefore can conduct electricity

Polar substances are soluble in polar solvents like water but are unable to dissolve in non polar solvents LIKE POLARITY DISSOLVES

Molecular substances have low melting and boiling points - due to weak intermolecular forces

Most are soft and easily scratched

27
Q

List some covalent network lattices

A

Diamond, silicon carbide, silicon dioxide and tungsten carbide

28
Q

What is a covalent network lattice

A

Where no molecules exist but atoms bond covalently in a three dimensional lattice structure

29
Q

What is diamond

A

Diamond is pure carbon that is in a covalent network lattice. Each carbon is held by strong covalent bonds and each carbon atom has four covalent bonds around it, this gives it three dimensional shape.

30
Q

List the properties of covalent network lattices

A

The lattices are usually quite hard and difficult to scratch and have high melting and boiling points - this is due to the very strong covalent bonds throughout the lattice structure

Covalent network lattice usually don’t conduct electricity in a solid form and liquid States - no moving ions

Chemically inert and insoluble in water and most solvents

Are brittle and of cut in a specific way they will shatter - bonds break if distorted

31
Q

What is a covalent layer lattice

A

Consists of countless atoms held together in a two dimensional plane by covalent bonds. These layers are then held together by dispersion forces.

32
Q

What is graphite

A

Black, oily, opaque solid.
Is made of carbon atoms
Forms three covalent bonds with other carbon atoms within the layer, this formed strong hexagonal rings.
One electron that isn’t being used becomes delocalised and is used for the dispersion forces to keep the layers together.
This electron can move across the layers

33
Q

List properties of graphite and explain them

A

Black, opaque, metallic sheen - due to the delocalised electrons reflecting the light

High melting point (>3000) - the bonds in each layer are so strong a large amount of energy is needed to break these bonds

Good conductor - due to the delocalised electrons are able to carry a charge down the countless layers

Soft, flakey, slippery - the weak dispersion forces allow the layers to slide past one another

34
Q

What are buckyballs, what is the most common formula

A

Are large cage like molecules of carbon covalently bonded atoms, not considered a lattice
C60

Solid at SLC
SOFT
RESISTANT TO COLLISION
LOW MELTING POINTS

35
Q

What are Nanotubes

A

Are continuous tubes of flat sheets of carbon atoms covalently bonded in a hexagonal ring

Similar to graphite but rolled into a cylinder

30 times stronger than steel but 1/5 as dense.

Are good thermal and electrical conductors

36
Q

List all properties to deduce whether a substance is a covalent molecular substance

A

Melting point - low
Hardness - soft
Conductivity in solid - poor
Conductivity in liquid - poor
Solubility in polar substances - soluble of polar
Solubility in non polar substances - soluble of non polar

37
Q

List the properties to deduce if the substance is a covalent network lattice

A

Melting point - very high
Hardness - hard
Conductivity in solid - poor
Conductivity in liquid - n/a
Solubility in polar substances - insoluble
Solubility in non polar substances - insoluble

38
Q

List all of the properties to deduce if a substance is a covalent layer lattice

A

Melting point - very high
Hardness - soft
Conductivity in solid - good
Conductivity in liquid - n/a
Solubility in polar substances - insoluble
Solubility in non polar substances - insoluble

Unit 1 Chemistry (4 decks)

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