Covalent bonding Flashcards

1
Q

What is a covalent bond?

A

Shared pair of electrons between two non-metals.

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2
Q

Pair of electrons in an atom not used up for covalent bonds are called what?

A

Lone pairs

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3
Q

What is an expansion of the Octet?

A

When an atom uses all the electrons in the 3d subshell form covalent bonds regardless of whether the atom ends up with a noble gas electronic configuration or not.

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4
Q

What is a dative/co-ordinate bond?

A

When a lone pair of electrons are used to form a covalent bond. The two electrons come from the same atom instead if different.

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5
Q

Dative/co-ordinate bond has the same what as covalent bonds?

A
  1. Length

2. Strength (average bond enthalapy)

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6
Q

The acceptor ion in a dative/co-ordinate bond must be what?

A

Electron deficient (have spaces for those electrons).

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7
Q

How do u show a dative/co-ordinate bond?

A
  • ->

eg. NH3 –> H

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8
Q

Shapes of molecules are based on what fact?

A

Electron pairs repel each other and move as part apart from each other as possible in order to minimise replusion.

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9
Q

Give shape name and angle for 2 total pairs

A

Linear 180*

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10
Q

Give shape name and angle for 3 total pairs

A

Trigonal planar 120*

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11
Q

Give shape name and angle for 4 total pairs

A

Tetrahedron 109.5*

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12
Q

Give shape name and angle for 5 total pairs

A

Trigonal bipyramidal 90/120*

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13
Q

Give shape name and angle for 6 total pairs

A

Octahedral 90*

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14
Q

What effect does lone pair have on bond angles and why?

A

Lone pairs repel more strongly than bonding pairs so each pair reduces the bonding angle by 2.5

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15
Q

Overall how to do the shape of molecules: (3steps)

A
  1. Find the base shape according to the total no. of pairs.
  2. Reduce the angles according to lone pairs.
  3. Ignore the lone pairs and find a new name of shape with the modified angles.
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16
Q

What is electronegativity?

A

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

17
Q

Describe and explain the trends of electronegativity across and down a group.

A
  1. Increases across a period (as atomic radius decreases and nuclear charge increases).
  2. Decreases down a group (as shielding increases)
18
Q

How is electronegativity measured?

A

Using a Pauling scale (1-4)

19
Q

Different between pure covalent bond and polar covalent bond.

A

In pure covalent bonds, the shared pair of electrons lie midway between the two equally electronegative nuclei. Whereas, in polar covalent bonds, the pair of electrons are attracted more towards a more electronegative nuclei causing a separation of charge (dipole) and creating an overall polarity (dipole moment).

20
Q

How is a polar bond shown.

A

S+ S-
S= small charge
–!–> points towards more electronegative element

21
Q

Give/explain 4 properties of simple molecular substances

A
  1. Low MP (weak intermolecular forces)
  2. Soft and breaks easily
  3. Does not conduct electricity( no charged ions to carry charge).
  4. Non-polar soluble in non-polar solvent and polar in polar solvent.
22
Q

Give 3 properties of diamond (macromolecular)

A
  1. Hard
  2. High MP/BP
  3. Does not conduct electricity (each C atom bonded to 4 other so no free charge).
23
Q

Give 3 properties of graphite (macromolecular)

A
  1. Soft (layers can slide)
  2. High MP/BP
  3. Does conduct electricity (Each carbon bonded to 3 other- free electron to carry charge).