P1: Bonding Flashcards by Chloe Coleman

Define Electronegativity

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

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What element has the highest electronegativity and why?

Fluorine
Has a small atomic radius so less shell shielding, but lots of protons so that it can strongly attract electrons.

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What is ionic bonding in terms of electronegativity?

Two extremes of electronegativity (opposite) to be pure.

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What is covalent bonding in terms of electronegativity?

Two almost equal amounts of electronegativity (pure)

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What is a covalent bond between?

Non metal atoms.

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What is an ionic bond between?

Metal and non metal atoms

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What is a Dative bond?

Occurs when one atom provides both of the electrons for the covalent bond.

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What does Isoelectronic mean?

Different elements, but the same electronic structure

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What is a bonding pair?

Two shared electrons in a covalent bond

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What is a lone pair?

Two electrons in a pair, not involved in bonding

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Explain the ‘Linear’ shape of a molecule

Flat, in the plane
Bond angle of 180º, as the are repelling as far away as possible
2 bonding pairs
0 lone pairs
e.g CO2
```
     ◦-●-○
```

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Explain the ‘Trigonal Planar’ shape of a molecule

-Flat, in the plane
-Bond angle of 120º
-3 bonding pairs
-0 lone pairs
-e.g BF3

-Upside down Y shape

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Explain the ‘Tetrahedral’ shape of a molecule

-2 bond in the plane, 2 bonds out of the plane
-Bond angle of 109.5º
-4 bonding pairs
-0 lone pairs
-e.g CH4

-so one bond will go towards me, one will go behind

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Explain the ‘Octahedral’ shape of a molecule

-2 bonds in the plane, 4 bonds out of the plane
-Bond angle of 90º
-6 bonding pairs
-0 lone pairs
-e.g SF6

-Top and bottom in the plane, two towards me, two going behind

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Explain the ‘Trigonal Bi-Pyramidal’ shape of a molecule

-3 bonds in the plane, 2 out of the plane
-Bond angle of 90º between the top and side bonds, and then 120º between the side bonds
-5 bonding pairs
-0 lone pairs
-e.g PF5

-Top, bottom and left in the plane, one towards, one behind

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By what degree does having a lone pair push the other bonds down by?

2.5º

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How are lone pairs different to bonding pairs in terms of repulsion?

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-Lone pairs are more compact and closer to the nucleus, which therefore means they provide more repulsion.
-The greatest repulsion comes from two lone pairs, and the weakest is two bonding pairs

Describe the ‘Trigonal Pyramidal’ shape of a molecule

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-3 bonding pairs
-1lone pair
- The lone pair at the top pushes the bond angles down by 2.5º. so its not 109.5º its actually 107º

-Lone pair at the top, one bond in the the plane, one towards, one behind

Describe the ‘Square planar’ shape of a molecule

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-4 bonding pairs
-2 lone pairs
-Still a bond angle of 90º (octahedral) because the lone pairs placement mean the forces even out and don’t change anything

Lone pairs at the top and bottom to be as far away from each other as possible, then 2 behind, 2 towards
Becomes a flat shape

Explain the ‘Non Linear’ shape of a molecule

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-e.g water
-2 lone pairs
-2 bonding pairs
-2 lone pairs which push the other bonds down, so it can be a straight shape, its bent
- Because these 2 lone pairs are next to each other at the top, their forces add together: 2.5+2.5= 5
-Therefore the bond angle is X-5
-104.5

-An upside down V shape, 2 lone pairs at the top, 2 bonds at the bottom

What are the properties of a metallic bond?

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-Melting point: Very high, electrostatic forces
-Conductivity solid: ✓ free electrons
-Conductivity liquid: ✓ free electrons
-Conductivity aqueous: ✗ insoluble
-Soluble in water: ✗

What are the properties of an ionic bond?

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-Melting point: High, electrostatic forces
-Conductivity Solid: ✗ no free electrons
-Conductivity Liquid: ✓ lattice is broken, ions can move
-Conductivity Aqueous: ✓ ions free to move
-Soluble in water: ✓ water breaks down lattice by getting in-between molecules

What are the properties of a simple molecular bond?

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-Melting point: Low, weak intermolecular forces
-Conductivity Solid: ✗ no free electrons or ions
-Conductivity Liquid: ✗
-Conductivity Aqueous: ✗
-Soluble in water: Depends on the molecule

What are the properties of a giant covalent molecule?

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Melting point: Very high, electrostatic forces
Conductivity Solid: ✗, apart from graphite
Conductivity Liquid: ✗
Conductivity Aqueous: ✗
Soluble in water: ✗, imissible

What are the elements that will form a polar bond?

Nitrogen (N), Oxygen (O), Fluorine (F), Chlorine (Cl), Bromine (Br) -Partially negative

Define what a 'polar bond' is

A covalent bond where the atoms have unequal attraction because one element is more electronegative than the other so is unequal; a dipole.

What does lowercase delta (d) mean?

Means a partial charge in a polar bond: therefore will be d- or d+

How do you show polar bonds?

-A partially negative sign (d-) next to the most electronegative element (one of N,O,F,Cl,Br) -A partially positive sign (d+) next to the other elements -An arrow going towards the negative (where the energy is going)

Describe 'Van der Waals' forces (VDW)

-AKA induced dipole-dipole forces -An instantaneous dipole is formed when the electron density in a molecule/atom is in an instant uneven due to movement of electrons, creating a non-permanent dipole. -This dipole can the induce a dipole in the next molecule along as the two negative charges will repel and create a partial positive charge. -Occurs in non-polar bonds -Weakest form of force

Describe a 'permanent dipole-dipole' force

-The attraction of a partial negative charge in one molecule attracting the partial positive charge of another molecule, creating a permanent attraction. -Occurs in polar bonds

Describe 'hydrogen bonding' forces

-Not an actual bond, its a force -A hydrogen atom bonded to a very electronegative element with a lone pair, so F, O, N -The hydrogen will be attracted to the lone pairs, where the force is. -This is the strongest type of intermolecular force. -Occurs in polar bonds e.g H-F attracted to :N-

What is the second type of 'Non-linear/bent' shape?

-2 bonding pairs -2 lone pairs -Bond angle: 118 looks like v upside down

Explain the 'Trigonal bi-pyramidal/seesaw' obscure shape

-4 bonding pairs -1 lone pair -Bond angle: 102 and 87 lone pair at top, bonding pairs in a fan shape at bottom

Explain the 'T-shaped' shape

-3 bonding pairs -2 lone pairs Bond angle: 88

Explain the linear obscure shape

-3 bonding pairs -2 lone pairs -bond angles: 180 2 lone pairs on one side 1 on the other

What is a step by step process of predicting a shape of a molecule?

1. Draw dot and cross diagrams 2. Count number of electron pairs around the central atom 3. Identify electron pair arrangement 4. Identify lone pairs and bonding pairs

Does electronegativity decrease or increase across a period?

Increase

Does electronegativity increase or decrease down a group?

Decrease

Why does Hydrogen have the same electronegativity as carbon (or very similar)?

It has no shielding

What is the Pauling scale?

-A numerical measure of electronegativity -Higher the value, the more electronegative the element is. A difference greater than 0.5 is a dipole/polar bond.

What are the rules when deciding if a molecule is polar?

1. No polar bonds= not a polar molecule 2. Polar bonds that are all on one side of central atom= polar molecule 3. Molecule with all the same type of polar bond e.g C-Cl= not polar, cancel out 4. Polar bonds, with at least one different type of polar bond= polar molecule

P1: Bonding Flashcards

(41 cards)