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Chemistry > Atomic structure and bonding > Flashcards

Atomic structure and bonding Flashcards

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1
Q

What is an atom?

A

The smallest particle of a chemical element

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2
Q

Ionisation Energy

A

The amount of energy needed to remove 1 mole of electrons from a mole of atoms, in the gaseous state

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3
Q

Factors that affect ionisation energy

A

Nuclear charge, shielding and distance from nucleus

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4
Q

Successive ionisation energies

A

The energy required to remove each electron in turn

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5
Q

What can a mass spectrometer be used for?

A

To find the relative abundance and mass/charge ratio of an element or compound

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6
Q

Why is the mass spectrometer a vacuum?

A

Prevent any particles being tested from colliding with molecules in the air

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7
Q

What is electrospray ionisation?

A

Sample dissolved in a volatile substance
Injected through a fine hypodermic needle
The tip of the needle is connected to the positive terminal of a high voltage power supply
The particles gain a proton and are ionised

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8
Q

What is electron impact ionisation?

A

The sample is vaporised
High energy electrons are fired at it from an electron gun
This will knock off an electron from each particle to form a positive ion

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9
Q

What is acceleration in a mass spectrometer?

A

Positive ions are attracted towards a negatively charged plate and accelerate towards it
Once accelerated, all ions have the same kinetic energy
The amount they accelerate depends on the mass to charge ratio of an ion

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10
Q

What is ion drift in a mass spectrometer?

A

Particles travel at different speeds due to their mass and start to drift apart

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11
Q

How are ions detected in a mass spectrometer?

A

Ions hit the detector and gain electrons which generates a current
The size of the current is proportional to the abundance of the ion

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12
Q

Why are sample particles ionised?

A

So they can be accelerated towards a negatively charged plate and gain electrons to generate a current when they hit the detector

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13
Q

How are ions accelerated in a mass spectrometer?

A

Positive ions attracted to negatively charged plate
All ions have the same kinetic energy

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14
Q

How are ions separated in a mass spectrometer?

A

Ions travelling at higher speeds (slower m/z ratio) move ahead of those travelling more slowly (large m/z ratio)

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15
Q

What is the relative atomic mass?

A

Average weighted mass of an atom relative to carbon 12

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16
Q

What is electronegativity?

A

The power of an atom to attract the pair of electrons in a covalent bond

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17
Q

How to work out if a molecule is polar?

A

Partial charges around the molecule change
So, asymmetrical
Dipoles do not cancel out
Permanent dipole
Polar

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18
Q

How to work out if a molecule is non-polar?

A

Partial charges around the molecule remain the same
So, symmetrical
Dipoles cancel out
No permanent dipole
Non-polar

19
Q

How does hydrogen bonding arise?

A

Large difference in electronegativity between the oxygen atom and the hydrogen atom of the OH bond
This polarises the OH bond
There is a strong attraction between the lone pair of Oxygen atom and partially positive hydrogen atom on another molecule

20
Q

How do permanent dipole-dipole forces arise?

A

There is a difference in electronegativity between the chlorine atom and hydrogen atom
This polarises the HCL bond forming a dipole
The dipoles do not cancel out as the molecule is asymmetrical
There is an attraction between the partial positive hydrogen atom and partial negative chlorine on another molecule

21
Q

How do induced dipole-dipole forces arise?

A

Random movement of electrons in a molecule causes an uneven distribution of electrons
This forms a temporary dipole
This induces a dipole in another molecule
There is an attraction between dipoles on neighbouring molecules

22
Q

What are the 4 properties of metals and why?

A

Good conductors of heat because delocalised electrons help transfer energy through the metal efficiently
Good conductors of electricity because delocalised electron can flow easily
Strong - strong electrostatic attraction between positive metal ions and delocalised electron
Malleable and ductile - rows of metal ions can slide past one another
High melting and point

23
Q

What is ionic bonding?

A

Strong electrostatic attraction between oppositely charged ions

24
Q

What is a covalent bond?

A

Shared pair of electrons between 2 atoms

25
Q

What is a coordinate bond?

A

Shaired pair of electrons with both electrons supplied by one atom

26
Q

What is ionic bonding?

A

Electrostatic attraction between oppositely charged ions in a lattice

27
Q

What is metallic bonding?

A

Attraction between positive metal ion and delocalised electrons arranged in a lattice

28
Q

What are macromolecular structures?

A

Covalent bonds extend throughout the entire structure

29
Q

What are the macromolecular structures?

A

Carbon
Silicon
Silicon oxide/dioxide

30
Q

Example of macromolecular crystals

A

Diamond
Graphite

31
Q

What are allotropes?

A

Different structural forms of the same element

32
Q

Describe the structure of a diamond

A

Each carbon has 4 covalent bonds
Tetrahedral shape repeated over the whole structure
High melting and boiling point
Non-conductors - no delocalised electron

33
Q

Describe the structure of graphite

A

Layers with 3 covalent bonds to each carbon
Each carbon has a delocalised electron - conducts electricity
Layers held together by weak intermolecular forces
Layers are far apart in comparison to covalent bond length - low density
Soft layers can slide over each other
High melting point

34
Q

What are simple molecular structures?

A

Made up of molecules

35
Q

Example of simple molecular structures

A

Iodine
NH3
H2O

36
Q

Describe the structure of iodine

A

Diatomic molecule with a single covalent bond
Solid iodine crystals are made up of a lattice of these I2 molecules
Each I2 molecule is held close to its neighbouring molecule by intermolecular forces

37
Q

Describe the strength of repulsion

A

Strongest: lone pair - lone pair
Lone pair - bond pair
Weakest: bond pair - bond pair

38
Q

What does electronegativity mean?

A

Power of an atom to attract the pair of electrons in a covalent bond

39
Q

What does polarity mean?

A

Unequal sharing of electrons between 2 atoms covalently bonded

40
Q

Explain the importance of hydrogen bonding in ice

A

Ice is less dense than water
Because the hydrogen bonds hold the molecules further apart

41
Q

Why is the boiling point of aluminium higher than silicon but the melting point of silicon is higher?

A

Silicon, once molten, only a little more energy is needed to vaporise it so the melting point of silicon is higher than its boiling point
Whereas, aluminium once molten a lot of energy is still needed to overcome strong electrostatic metallic bonds so aluminium has a high boiling point

42
Q

Suggest why magnesium is a liquid over a much greater temperature range compared to bromine

A

Liquid Mg has strong electrostatic attractions between delocalised electrons and metal ions which still require a lot of energy to break

43
Q

Why does I2 have a higher boiling point than HCl

A

Iodine has more electrons than HCl
Greater energy required to overcome the Van Der Waals in I2

44
Q

Identify the s-block metal that has the highest first ionisation energy

A

Be

Chemistry (28 decks)

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