OZ - Electronegativity Flashcards

1
Q

What is electronegativity?

A

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

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2
Q

What is electronegativity usually measured using?

A

The Pauling scale.

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3
Q

What does the size of the electronegativity value suggest about the electronegativity of the element?

A

The higher the electronegativity value, the more electronegative the element.

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4
Q

What is the most electronegative element?

A

Fluorine - has a value of 4 on the Pauling scale.

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5
Q

Apart from fluorine, what other elements are also very strongly electronegative?

A

Oxygen, chlorine and nitrogen.

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6
Q

How high is the value of the most electronegative element?

A

4.0

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7
Q

How low is the value of the least electronegative element?

A

Around 0.7

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8
Q

How does electronegativity change across the periodic table?

A

It increases as you move towards fluorine.

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9
Q

How does electronegativity change across periods?

A

Increases.

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10
Q

How does electronegativity change down groups?

A

Decreases (ignoring the noble gases).

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11
Q

What might covalent bonds be polarised by?

A

Difference in electronegativity.

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12
Q

In covalent bonding, where do the bonding electrons sit?

A

In orbitals between 2 nuclei.

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13
Q

When will covalent bonds be non-polar?

A

If both atoms have similar or identical electronegativities and so the electrons will sit roughly midway between the 2 nuclei and the bond will be non-polar.

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14
Q

In what molecules will covalent bonds be non-polar and why?

A

In homonuclear, diatomic gases (e.g. H2 and Cl2) because the atoms have equal electronegativities and so the electrons are equally attracted to both nuclei.

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15
Q

When will covalent bonds be polar?

A

If the bond is between 2 atoms with different electronegativities making the bonding electrons get pulled towards the more electronegative atom. This causes the electrons to be spread unevenly and so there will be a charge across the bond (each atom has a partial charge - one atom is slightly positive and the other is slightly negative).

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16
Q

How do you work out if a bond is polar or not?

A

By using the Pauling scale:

Find the difference between the electronegativity values given for each atom in the bond. The bond is polar if the difference in electronegativity values is more than about 0.4.

17
Q

What difference in electronegativity value using the Pauling scale shows a polar bond?

A

The bond is polar if the difference in electronegativity values is more than about 0.4.

18
Q

In a polar bond, what does the difference in electronegativity between the 2 atoms cause?

A

A dipole.

19
Q

What is a dipole?

A

A difference in charge between the 2 atoms caused by a shift in electron density in the bond.

20
Q

What is a dipole caused by?

A

A shift in electron density in the bond.

21
Q

Finish this sentence with the effects on electron density and and the polarity of the bond:

The greater the difference in electronegativity…

A

…the greater the shift in electron density, and the more polar the bond.

22
Q

Whether a molecule is polar or not depends on what?

A

Its shape and the polarity of its bonds.

23
Q

What does a polar molecule have?

A

An overall dipole, which is just a dipole caused by the presence of a permanent change across the molecule.

24
Q

What is an overall dipole?

A

A dipole caused by the presence of a permanent charge across the molecule.

25
Q

What might an overall dipole also be referred to as?

A

‘Overall polarity’.

26
Q

If the polar bonds are arranged so they point in opposite directions, does it mean the molecule is polar or not?

A

Non-polar as they’ll cancel each other out.

27
Q

If the polar bonds are arranged so they all point in roughly the same direction, does it mean the molecule is polar or not?

A

Polar.