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Chemistry Term 1 > Electronegativity > Flashcards

Electronegativity Flashcards

1
Q

What is electronegativity?

A

The ability of an atom to attract the bonding electrons in a covalent bond

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2
Q

What three things is an atom’s electronegativity affected by?

A

1) Nuclear Charge
2) Size of an atom
3) Location of shared pair of electrons

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3
Q

How is electronegativity measured?

A

The Pauling scale

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4
Q

What do large values on the Pauling scale indicate?

A

Atoms are very electronegative

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5
Q

What bond type is an electronegativity difference of 0 for?

A

A pure covalent bond

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6
Q

What bond type is an electronegativity difference of 0-1.8 for?

A

A polar covalent bond

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7
Q

What bond type is an electronegativity difference of 1.8< ?

A

Ionic bond

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8
Q

What collection of molecules have pure covalent bonds?

A

Diatomic molecules

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9
Q

Why are hydrocarbons non-polar molecules?

A

C and H have very similar electronegativity values so there is an even distribution of electrons

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10
Q

What four elements are most electronegative?

A

Nitrogen, Oxygen, Fluorine, Chlorine

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11
Q

Where are the most electronegative elements?

A

Furthest right and furthest up the periodic table (excluding noble gases)

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12
Q

What characteristic does a non-polar molecule have?

A

It’s molecule is symmetrical so the dipoles in either direction cancel out

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13
Q

What are intermolecular forces?

A

The forces between molecules

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14
Q

What is a simple molecular lattice?

A

Molecules held in arrangement by weak forces

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15
Q

What forces are the weakest?

A

London forces

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16
Q

What forces are the second weakest?

A

Permanent dipole-dipole interactions

17
Q

What forces are the strongest?

A

Hydrogen bonds

18
Q

What is the permanent dipole-dipole interactions between?

A

A partially positive charged atom of one molecule and a partially negative charged atom of another molecule

19
Q

What molecule demonstrates dipole-dipole interactions?

A

HCl

20
Q

Are London forces instantaneous?

A

Yes - they are always changinf

21
Q

Why are London forces weak?

A

They are only slightly charged at any point

22
Q

What do instantaneous dipoles induce in neighbouring molecules?

A

Induced dipoles

23
Q

What two types of molecules can London forces occur between?

A

1) non-polar molecules
2) non-polar with permanent dipoles

24
Q

How does a molecules london forces change when there is an increasing number of electrons? Why?

A

They increase as there are more induced dipoles

25
Q

How would stronger london forces affect the boiling/ melting point?

A

Increases them as more energy is needed to overcome them

26
Q

How is the negative charge around a covalent bond distributed?

A

Not evenly

27
Q

How does electronegativity vary across a period?

A

It Increases along a period as the atomic radius decreases and charge density increases.

28
Q

How does electronegativity vary down a group?

A

It decreases - shielding increase so atomic radius increases so charge density decreases

29
Q

How can polar molecules with a permanent dipole align?

A

To form a lattice of molecules similar to an ionic lattice

30
Q

Why do straight chain molecule’s experience stronger London forces?

A

They can pack closer together, reducing the distance over which the force acts, making it stronger

31
Q

Why do longer alkane chains have higher boiling points?

A

They have a larger Mr, so stronger London forces between chains

32
Q

Why does branching of alkane chains cause for weaker London forces?

A

The chains are less able to pack tightly together so the distance the forces act is increased and the attractive forces are weakened - lower boiling point.

33
Q

What do hydrogen bonds act between? (Exclusively)

A

Between hydrogen and either nitrogen, oxygen or fluorine (most electronegative atoms)

34
Q

How is a hydrogen bond demonstrated in a diagram?

A

A dotted line

35
Q

Why does ice have a Lower density than liquid water?

A

The hydrogen bonds hold the molecules in a rigid structure with a lot of air gaps

36
Q

Why are water and alcohols not good at dissolving polar molecules?

A

Some can’t form hydrogen bonds

Chemistry Term 1 (8 decks)

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