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Higher Chemistry Prelim > Unit 1 Chemical changes and structure > Flashcards

Unit 1 Chemical changes and structure Flashcards

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1
Q

What is meant by covalent radius?

A

Covalent radius describes half of the distance between two atoms in a covalent bond.

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2
Q

What happens to the covalent radius as you go across a period of the periodic table?

A

As you go across the periods of the periodic table the number of protons in each element increases this decreases the covalent radius of the elements.

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3
Q

What happens to the covalent radius of atoms as you go down a group?

A

As you go down a group the number of electron shells increases, this increases the covalent radius

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4
Q

What is meant by the term Electronegativity?

A

Electronegativity can be defined as the measure of an atom involved in a bond to attract bonding electrons

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5
Q

What can be said about an atom with a high electronegativity value?

A

An atom with a high electronegativity value has a strong attraction for bonding electrons

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6
Q

What can be said about an atom that has a low electronegativity value?

A

An atom with a low electronegativity value has a weak attraction for bonding electrons.

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7
Q

What happens to electronegativity values as you go down a group in the periodic table?

A

As you go down a group number of electron shells increases this increases the shielding effect that causes the attraction for bonding electrons to decreases

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8
Q

What happens to electronegativity values as you go across a period in the periodic table?

A

As you go across a period the number of protons increases this causes an increased attraction for negatively charged bonding electrons

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9
Q

What is meant by the term ionisation energy?

A

Ionisation energy can be described as the energy required to remove one mole of electrons from one mole of gaseous atoms or ions

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10
Q

What must you remember to do when you are writing out an ionisation energy equation?

A

The element must have a gaseous state symbol and the electron that is removed must be shown on the right hand of the equation

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11
Q

What happens to the ionisation energy as you go across a period in the periodic table?

A

As you go across a period of the periodic table number of electrons increases this causes the first ionisation energy to increase as the forces holding the electron in orbit of the atoms molecule have increased.

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12
Q

What happens to the first ionisation energy of an atom as you go down a group in the periodic table?

A

As you go down a group in the periodic table the number electrons shells increases, this increases the shielding effect causing the outermost electrons to be more easy to remove resulting in a lower first ionisation energy as the force acting on the electrons in the outermost shell is decreased

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13
Q

Why is the second ionisation energy always larger than the first?

A

Since after the first ionisation of the atom the number of protons has stayed the same however the number of electrons has decreased meaning more force acts on the remaining electrons

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14
Q

Why is the second ionisation energy of lithium so much larger than other gaps between first and second ionisation energies?

A

Since the second ionisation of lithium requires breaking into a very stable complete outermost electron shell which requires a great deal of additional energy to remove the electron

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15
Q

What will adding first and second ionisation energies do?

A

Give the resulting energy required to remove multiple moles of electrons from a mole of gaseous atoms

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16
Q

Which type of bonding does not exist in elements?

A

Ionic bonding does not exist in elements as Ionic bonding requires a large difference in electronegativity between atoms

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17
Q

What are the elements that exist as a covalent network in elements?

A
  • Boron
  • Silicon
  • Carbon
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18
Q

What are the different types of bonding that are in elements?

A
  • Metallic lattice
  • Covalent Network
  • Covalent molecular
  • Monatomic gasses
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19
Q

What are the properties of monatomic gases?

A

Molecules are held together by the intermolecular forces: London dispersion forces, They do not conduct electricity and have very low melting and boiling points such that all elements exist as gases at room temperature

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20
Q

What are some of the properties of Covalent networks?

A

Covalent networks have strong covalent bonds through their structure and have no intermolecular forces for this reason they have very high melting and boiling points and do not conduct electricity

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21
Q

What are the properties of Covalent molecular elements?

A

They have strong covalent bonds holding atoms together however have weak intermolecular forces called london dispersion forces, this causes them to have low melting and boiling points. Covalent substances do not conduct electricity as the atoms are held in place

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22
Q

What are some of the properties of metallic lattice elements?

A

They have very strong metallic bonds and for this reason they have high melting and boiling points. They are able to conduct electricity because of the delocalised electrons contained in their lattice structure

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23
Q

What happens to the strength of a london dispersion force as the number of electrons increases?

A

As the number of electrons increases this increases the strength of the london dispersion forces as the strength of the temporary dipole increases which increases the strength of the induced dipole.

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24
Q

Define what is meant by a molecular element?

A

A molecular element is an element that can exist as molecules of itself

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25
Q

What are the two types of molecular elements?

A
  • Diatomic elements
  • Polyatomic elements
26
Q

Name the Diatomic elements?

A
  • Hydrogen
  • Nitrogen
  • Oxygen
  • Fluorine
  • Chlorine
  • Bromine
  • Iodine
27
Q

Name the Polyatomic elements and give their chemical formulae?

A
  • Phosphorus (P4)
  • Sulfur (S8)
  • Carbon as Fullerine (C60)
28
Q

What happens to the covalent bonds when a state change of a solid covalent molecular element turns to a liquid?

A

The strong covalent bonds do not influence the melting or boiling point of the molecule, instead the weak london dispersion forces are broken down in a state change

29
Q

What happens to the melting points of the polyatomic elements as you go from phosphorus to fullerine?

A

The melting and boiling points increase as the strength of the london dispersion forces increases due to the increased number of atoms and therefore more electrons

30
Q

What does the breakdown of weak london dispersion forces in molecules do?

A

The molecules move further apart from one another

31
Q

What is the idea of a bonding continuum?

A

The bonding continuum is an idea that places pure covalent and Ionic substances at opposite ends of a spectrum. Where a chemical lies of the bonding continuum depends on the difference in the electronegativity values of the elements in the bond

32
Q

What charge will an element with the higher electronegativity in a bond have?

A

A higher electronegativity value will cause the element to be negatively charged as it has a stronger attraction for the electrons in the bond

33
Q

What happens to the atoms with a smaller electronegativity value?

A

A smaller electronegativity value will cause an atom to be positively charged as it will have a lower attraction to atoms in the bond

34
Q

What does the polarity of a molecule effect about that molecule?

A
  • Strength of the bonds in the molecule
  • Type of bonding present in the molecules
  • Properties that the molecule will have (viscosity/solubility)
35
Q

What is a van der waals force?

A

A van der waals force is any intermolecular force that is caused by dipole interactions

36
Q

What are the three types of van der waals force?

A
  • London dispersion forces
  • PDPD interactions
  • Hydrogen bonding
37
Q

What are the conditions that must be met for a molecule to be polar?

A
  • The molecule must have polar bonds
  • The molecule must have a 3D shape in which the dipoles created by the polar bonds are not cancelled out
38
Q

If we have two liquids one is polar and the other is non-polar can you explain one way of identifying which molecules are polar?

A

Running the liquids through a tap and placing a charged rod next to both, the polar molecules will be deflected by the charge as polar molecules have charged dipoles

39
Q

What type of Intermolecular forces are present in non-polar molecules?

A

Non-polar molecules contain london dispersion forces that increase in strength as the atomic size increases (because this increases the number of electrons and strength of the dipoles increase)

40
Q

What types of bonding are present in polar molecules and when does each type of bonding occur?

A
  • Permanent dipole interactions, these are caused by the attractions between the permanent dipoles in different atoms this occurs because each dipole in a polar molecule is fixed unlike the temporary dipoles present in non-polar molecules
  • Hydrogen bonding, this type of bonding occurs in a particularly polar bond and occurs only when a hydrogen atom is directly attached to either a Nitrogen atom, Oxgyen atom, or a Flourine atom.
41
Q

What elements can hydrogen be directly attached to when forming a hydrogen bond?

A
  • Nitrogen
  • Oxygen
  • Fluorine
42
Q

Name the van der waals forces in order of weakest to strongest?

A

london dispersion forces, permanent dipole permanent dipole interactions, hydrogen bonding

43
Q

What precautions must be taken when we are comparing different van der waals forces?

A

When comparing different van der waals forces the GFM of the compounds should be kept roughly the same to ensure that any difference in melting or boiling point is caused by the forces that are being investigated and not just because of the increased number of london dispersion forces in one of the chemicals

44
Q

Why are molecules with high amounts of hydrocarbon character predominantly held together by london dispersion forces?

A

Because molecules with high hydrocarbon character the dipoles cancel one another out so most of the bonds are non-polar and the molecules can be very large this increases the strength of the london dispersion forces present

45
Q

What is meant by the term viscosity?

A

Viscosity is a measure of how easily a liquid resists flow

46
Q

What can be said about a highly viscous liquid?

A

It will not resist flow and will run easily

47
Q

What can be said about a liquid with a low viscosity?

A

It will resist flow and appear runny

48
Q

What is the general rule that links viscosity to the intermolecular forces present?

A

As the intermolecular forces present increase the viscosity of the liquid will also increase

49
Q

What situation is described with the term miscible?

A

When two liquids mix with one another

50
Q

What situation describes the term immiscible?

A

When two liquids do not mix with one another

51
Q

What relation does intermolecular bonding have to the solubility of a molecule?

A

Molecules with the same type of intermolecular bonding as their solvent are more likely to dissolve into that solvent

52
Q

What us meant by a reduction reaction?

A

A reduction reaction is where an ion gains electrons to become an atom

53
Q

What is an oxidation reaction?

A

A reaction in which electrons are lost

54
Q

What is the reaction called when reduction and oxidation occur at the same time?

A

a redox reaction

55
Q

What is the reducing agent?

A

The species that donates electrons to reduce the other species in the reaction

56
Q

What is the oxidising agent?

A

The oxidising agent is the agent that accepts electrons from the other species allowing it to undergo oxidation

57
Q

What type of agent are elements with high electronegativity values likely to be?

A

Elements with high electronegativity values are likely to be oxidising agents as they have a stronger attraction for electrons

58
Q

What type of agent are elements with a low electronegativity value likely to be?

A

Reducing agents as they have a weak attraction for bonding electrons meaning that they are more easily donated to the other species

59
Q

Where in the electrochemical series can we find the best oxidising agents as the best reducing agents?

A
  • The best reducing agents can be found on the high right of the electrochemical series
  • The best oxidising agent can be found on the bottom left of the electrochemical series
60
Q

What is volumetric analysis?

A

A technique that uses titration and allows us to determine the mass or concentration of a chemical substance

61
Q

What is a standard solution?

A

A solution with an accurately known concentration

Higher Chemistry Prelim (3 decks)

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