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Key Concepts In Chemistry Flashcards

1
Q

What are ionic bonds?

A
  • Strong electrostatic forces of attraction
  • Between oppositely charged ions
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2
Q

Do ionic compounds usually have high or low melting points and why?

A
  • High
  • Many strong ionic bonds so large amounts of energy must be transferred to lattice structure to break these bonds
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3
Q

Are ionic compounds usually soluble in water?

A

Yes they dissolve to form aqueous solutions

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4
Q

Do you giant molecular substances usually have high or low melting points?

A

High, a lot of energy must be transferred to break string covalent bonds

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5
Q

In a non-enclosed system, what will happen to the mass of a reactive metal it is heated in air?

A

Increase - because oxygen atoms in the air will combine with metal atoms to form a metal oxide

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6
Q

In a non-enclosed system what will happen to the mass of a reactive non-metal or a fuel if it is heated in air?

A

Decrease - because products in the gas state will escape from the container

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7
Q

In a non-enclosed system what will happen to the mass of a metal carbonate if it is heated?

A

Decrease - because carbon dioxide gas is produced and this escapes from the container

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8
Q

What is Avogadro’s constant?

A

6.02 x 10^23

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9
Q

Which elements are written with a subscript number 2?

A
  • Iodine
  • Bromine
  • Chlorine
  • Fluorine
  • Oxygen
  • Nitrogen
  • Hydrogen
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10
Q

What did Dalton’s ideas state about the atom?

A
  • Solid atom model
  • Atoms cannot be broken down into anything simpler
  • The atoms of an element are identical to each other
  • The atoms of different elements are different from each other
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11
Q

How did the model of the atom change?

A
  • Thompson: discovered the electron
  • Thompson: plum pudding model, spheres of positive charge with negative electrons dotted inside
  • Rutherford: solar system model, positive nucleus surrounded by negative electrons in orbits
  • Bohr: electron shell model, electrons occupy shells or energy levels around the nucleus
  • Rutherford: discovered the proton
  • Chadwick: discovered the neutron
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12
Q

What is the relative mass of an electron?

A

1 / 1836

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13
Q

How do you calculate the relative atomic mass of an element?

A

(Mass number of first isotope x abundance)
+
(mass number of second isotope x abundance)
/ 100

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14
Q

How did Mendeleev arrange the elements in his periodic table?

A
  • In order of increasing relative atomic masses
  • He noted that the chemical properties of the elements and showed a trend
  • He swapped the places of some elements so that elements with similar properties lined up
  • He left gaps we thought there were other elements and predicted their chemical and physical properties (they were very accurate)
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15
Q

Why did Mendeleev put tellurium in group 6 and iodine in group 7?

A
  • He did not know about isotopes
  • Iodine has one naturally occurring isotope, iodine–127
  • The most abundant tellurium isotopes are tellurium-128 and tellurium-130
  • This means the relative atomic mass of tellurium is greater than iodine
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16
Q

How does the electronic configuration of an element determine which period it is in?

A

The number of occupied shells

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17
Q

How does the electronic configuration of an element determine what group it is in?

A

The number of electrons in the outer shell (except for group 0 which have full outer shells)

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18
Q

Are cations positive or negative?

A

Positive

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19
Q

Are anions positive or negative?

A

Negative

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20
Q

Do ionic compounds conduct electricity and why?

A
  • Yes, but only when molten or dissolved in water
  • These processes make the ions free to move
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21
Q

How do you name positively charged ions formed from hydrogen or metal atoms?

A

They take the name of the element

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22
Q

How do you name negatively charged ions formed from single non-metal atoms?

A

They take the name of the element the end in –ide

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23
Q

How do you name negatively charged ions in compounds containing three or more elements, one of which is oxygen?

A

They end in -ate

OH- does not follow this rule (hydroxide)

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24
Q

Do simple molecular substances usually have low or high boiling points and why?

A
  • Low
  • Although they have strong covalent bonds between atoms
  • There are weak intermolecular forces between molecules which can easily be overcome
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25
Do simple molecular substances conduct electricity and why?
- No - They have no overall charge, or any charged particles that can separate
26
What is the typical size of an atom?
1 x 10^-10
27
What is the typical size of a simple molecule?
1 x 10^-9
28
Are simple molecular substances soluble and why?
- No many are not - Because the intermolecular forces between water and the substances are weaker than those between water molecules and the molecules of the substance itself - They can if they form strong enough attractions with water molecules
29
Do giant molecular substances usually have low or high boiling point and why?
- High - A lot of energy must be transferred to break the many strong covalent bonds
30
Do giant covalent substances conduct electricity and why?
- No - They have no overall charge - Graphite is an exception
31
What is the structure of diamond?
- Each carbon atom is bonded to 4 others by covalent bonds - The atoms form a regular tetrahedral network structure - There are no free electrons
32
What is the structure of graphite?
- Each carbon atom is bonded to 3 others by covalent bonds - The atoms form a hexagonal layered network structure - The layers have weak intermolecular forces between them so they can slide - The unbonded electrons are delocalised so are free to move
33
Why is graphite used to make electrodes and lubricants?
- Electrodes because it has delocalised electrons to conduct electricity - Lubricant is because the layers can slide over each other so it is slippery
34
Why is diamond used to make cutting tools?
It has a rigid lattice structure and a strong covalent bonds so it is very hard
35
What useful properties does graphene have?
- Conduct electricity because it has delocalised electrons that can move through the structure - Strong and flexible because it contains many strong covalent bonds - Almost transparent because its layers are just one atom thick
36
What are fullerenes?
- They resemble a sheet of Graphene rolled to form buckyballs or nanotubes
37
What properties do materials made from buckyballs have?
- Conduct electricity because they have delocalised electrons - Are soft when solid because they have weak intermolecular forces
38
What properties do nanotubes have?
- Conduct electricity because they have delocalised electrons - Have high tensile strength because the structure has many strong covalent bonds
39
How many carbon atoms does buckminsterfullerene have?
60
40
What is the structure of polyethene?
Consists of large molecules containing chains of carbon atoms which are joined together and to hydrogen atoms by covalent bonds
41
What are the typical properties of metals?
- Shiny - Good electrical conductors - High melting points (not mercury) - High density - Good heat conductors - Malleable 
42
What are the typical properties of nonmetals?
- Dull - Poor electrical conductors (not graphite) - Low density - Low melting points (not graphite) - Poor heat conductors - Brittle
43
What is the structure of metallic bonding?
- Giant lattice of positively charged metal ions - ‘Sea’ of delocalised electrons - Strong electrostatic forces of attraction between them
44
Why are metals malleable?
- Layers of positive ions can slide over each other - This allows the metal to change shape without shattering
45
Why do metals conduct electricity?
They have delocalised electrons which can move through the structure of the metal
46
What are the limitations of the space filling models?
- Does not show how covalent bonds are formed - Does not show which elements are present (unless given at colour key) - You may not be able to see all the atoms if the model is complex
47
What are the limitations of ball and stick models?
- Does not show how covalent bonds are formed (the bonding and non-bonding electrons) - Bonds are shown as sticks rather than forces
48
What are the limitations of structure models for simple molecular substances?
- Does not show the relative sizes of the atoms - Does not show how covalent bonds are formed (the bonding and non-bonding electrons) - Does not show the relative sizes of the atoms
49
What are the limitations of dot and cross diagrams for simple molecular substances?
- Does not show the intermolecular forces - Does not show the relative sizes of the atoms
50
What are the limitations of chemical formula for simple molecular substances?
- Does not show the type of bonding - Does not show the shape of the molecule
51
What are the limitations of empirical formula?
- Does not show how the atoms are arranged - Does not show the actual number of atoms usually
52
What are the limitations of 2D diagrams for ionic bonding?
- Does not show how ions were formed - Does not show more than one layer
53
What are the limitations of 3D diagrams for ionic bonding?
- Does not show the charges - Does not show that there are no spaces between ions
54
What are the limitations of dot and cross diagrams for ionic bonding?
- Does not show the lattice structure - Does not show the ionic bonds
55
What is the empirical formula of a substance?
The simplest whole number ratio of the atoms of each element in a compound
56
How do you calculate an empirical formula?
- Write down the symbol of each element - For each element calculate mass divided by relative atomic mass - Divide each answer by the smallest answer - Multiply (if needed) to get whole numbers
57
How do you convert empirical formula to molecular formula?
- Calculate the relative formula mass of the empirical formula - Divide the relative formula mass given by the relative formula mass of the empirical formula - Multiply each number in the empirical formula by the answer
58
Experiment: how do you determine the empirical formula mass of magnesium oxide?
- Measure and record the mass of an empty crucible with its lid - Put a length of magnesium ribbon into it - Measure and record the total mass of the crucible, it’s a lid and contents - Place to crucible on a tripod with a pipeclay triangle, strongly heat for several minutes using a Bunsen burner - When the magnesium has stopped glowing, turn off the Bunsen burner and allow the Crucible to cool - Measure the total mass again
59
What are some examples of reactions in closed systems?
- Reactions in a sealed container - Precipitation reactions, where two soluble reactants from the insoluble precipitate
60
What is the stoichiometry of a reaction?
The ratio of the amount of each substance in a balanced chemical equation.
61
How do you calculate concentration?
Mass of solute (g) / Volume of solution (dm³)
62
What is a solution?
A mixture of a solute in a solvent
63
What is a solute?
The dissolved substance in a solution
64
What is a solvent?
The liquid which the solute dissolves in
65
How do you convert cm³ into dm³ ?
Divide by 1000
66
How do you calculate the number of moles in a substance?
Mass (g) / Relative atomic mass

Chemistry 🧬 (8 decks)

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