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Unit 1 higher Flashcards

1
Q

Activated complex

A

the activated complex is a very unstable arrangement of atoms

formed at the maximum of the potential energy barrier, during a chemical reaction

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2
Q

Activation energy

A

is the minimum kinetic energy required by colliding particles before reaction will occur

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3
Q

Allotrope

A

one of two or more existing forms of an element

E.g diamond

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4
Q

Collision theory

A

for a chemical reaction to occur, particles must collide

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5
Q

Covalent bond

A

Shared pair of electrons between non-metals

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6
Q

Covalent radius

A

half the distance between the nuclei of two bonded atoms of an element

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7
Q

Delocalised

A

Electrons or ions that are free to move im metallic and ionic bonds

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8
Q

Desorption

A

occurs when the bonds between the molecules and the surface break and the molecules leave the surface of the catalyst

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9
Q

Dipole

A

atom or molecule in which a concentration of positive charges is separated from a concentration of negative charge

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10
Q

Electronegativity

A

measure of the attraction that an atom involved in a bond has for the electrons of the bond

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11
Q

Enthalpy change

A

change in heat energy

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12
Q

Hydrogen bonds

A 
Percent dipole - dipole interactions 
Strongest type of intermolecular bond
Occurs when hydrogen atoms is covalently bonded to a highly electrgravitive element
Oppositely charged end attract
Eg water, ammonia, alcohols
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13
Q

Intermolecular forces

A

forces of attraction which exist within a molecule

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14
Q

Ionisation energy

A

energy required to remove one mole of electrons from one mole of atoms in the gaseous state

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15
Q

Isoelectronic

A

having the same arrangement of electrons

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16
Q

London dispersion forces

A

Weakest type of intermolecular bond
Between atoms and molecules
Molecular elements (eg oxygen) + monatomic elements (eg noble gases) will form solids if cooled at sufficiently low temp, freeze at absolute 0
Caused by uneven distribution of electrons within an atom
Temporary dipoles form

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17
Q

Lone pairs

A

pairs of electrons in the outer shell of an atom which take no part in bonding

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18
Q

Polar covalent bond

A

covalent bond between atoms of different electronegativity/elements
uneven distribution of electrons
Soluble in water + polar covalent

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19
Q

Ways a coarse of a reaction cab be followed

A

Gas produced
Change in mass
Change in temp
Change in colour

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20
Q

Relative rate

A

1/t

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21
Q

Average rate

A

Change in quantity/change in time

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22
Q

Why is it important to industry to be able to control the rate of a chemical reaction

A

If the rate is too low it may not be economically viable

If the rate is too hi there is a risk of thermal explosion

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23
Q

Variables that can affect rate of reaction

A 
Temp
Collision geometry
Catalyst
Pressure
Surface area 
Concentration
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24
Q

Is enthalpy change positive or negative in a exothermic chemical reaction

A

Positive

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25
Is the enthalpy change of and endothermic reaction positive or negative
Negative
26
Change in enthalpy =
Ep - Ea
27
Kinetic energy
The energy in a moving object
28
How does a catalyst speed up the rate of a chemical reaction
Lowers the activation energy so the particles need less energy for the reaction to occur
29
When there is an increase in temperate on how does it affect the energy distribution diagram
The higher temperature means particles have more Kentucky energy decreasing the activation energy
30
Repulsive force pretiöses must overcome is due to
Repulsive force from outer electrons
31
Collision geometry
The particles must face the right way so the activated complex can be formed
32
Periodic table (ionisation energy)
Horizontal - increases | Vertical - decreasing
33
Periodic table (covalent radius)
Horizontal - decreases | Vertical - increases
34
Periodic table (electron gravity)
Horizontal - increases | Vertical- decreases
35
Pure covalent bonds
Excites between 2 atoms with the same electron gravities No ionic character E.g diatomic elements Electrons shared equally
36
Ionic bonding
Uneven share of electrons (even more than polar covalent) Large difference in electron gravity Between metal + non-metal Element with larger electron gravity pulls electrons from smaller element High mp/BP Soluble in water + polar covalent Solvents
37
Difference in electron gravity most to least
Ionic - high Polar covalent - low Pure covalent zero
38
Van der walls forces
Intermolecular forces
39
Permanent dipole permanent dipole interactions
``` Molecules with a permanent dipole Attraction between the oppositely charged end of molecules Molecules are unsymmetrical Stronger than london dispersion forces Form permanent dipole ```
40
Bonding strengths low to high
Loben dispersions forces Permanent dipole interactions Hydrogen bonds Covalent bonds
41
properties of water
Ice less dense than water ( because water expands as it is frozen ) High surface tension - iron pin floats on water + how insects walk on water relatively high viscosity
42
Why do metallic bonds conduct electricity
When atoms loose one or more electrons they become positively charged Ions are now attracted to the pool of electrons These electrons are now free to move Causing them to conduct
43
Why does aluminium conduct better than sodium
Aluminium has three outer electrons whereas sodium has one, when theses electrons delocalise aluminium has a higher conductivity
44
Why do metals shine in sunlight
Metal absorbs light energy and re-emits it
45
What intermolecular forces does covalent bonds have
Non-polar
46
How does graphite conduct electricity
Delocalised electrons are held weakly, that can flow across layers
47
Covalent network structures
Diamond Carbon graphite Silicon Boron
48
What happens when noble gases have electricity pass through them
They emit light | Eg outdoor signs
49
Factors considered to see atomic size
Nuclear charge on an atom | The number of filled electron shells
50
Ionisation energy factors must be considered
The nuclear charge of the atom The number of filled electron shells The size of the atom
51
Electron gravity factors must be considered
The nuclear charge of an atom The number of filled electron shells The size of the atom
52
What increases when a chlorine atom becomes a chlorine ion
The number of full energy levels
53
Why does electron gravity increase across the period table
Positive nuclear charges increases
54
Which element has the highest electron gravity value
Fluorine
55
Why is there an increase in covalent radius going down a group
Increase in the number of electron shells
56
Why does covalent radius decrease going across a period
The number of nuclear charge increases
57
Why does the first ionisation energy of elements tend to decrease as you go down a group
Number of electron shells increase | Outer electrons are less stronger held
58
Why first ionisation energy of elements tend to increase as you go across period
Number of nuclear charge increases | Pulls the outer electron close to the nucleus
59
How can ionic bonds form covalent bonds
By sharing electrons
60
What do more electron gravities elements do
Elect with greater value of electron gravity is more likely to gain electrons from a negative ion and the element with the smaller value is most likely to loose electron forming a positive ion
61
How to tell if an element is covalent or ionic
If the tall charge of ions is 0 then it is ionic bonding
62
Boiling points of polar and non-polar compounds
Polar has higher boiling point and higher viscosity than non-polar
63
Thermite reaction
Highly exothermic reaction | Displacement reaction
64
Reducing agents
Substance which donates electrons | Elements with low electron gravity
65
Oxidising agent
Substance which accepts electrons | Elements with high electron gravity
66
Why does boiling point increase going down group 7
The number of occupied electron shells increases Increasing the number of electrons Increasing the strength of LDF’s between molecules Requiring more energy to break
67
Explain fully the increase between the 5th and the 6t ionisation energy of carbon
The state first energy level with 2 electrons is being broken so more energy is required
68
Why does the ionic radius of phosphorus greater than aluminium
Phosphors has more outer electrons and is negatively charged, this attracts the electrons from aluminium more strongly
69
Why does ammonia have a high melting point
Ammonia has. Hydrogen bonding The nitrogen is bonded to hydrogen LDF’s between molecules are extremely strong Requires a lot of energy to break
70
Covalent bonds
Shared par of electrons between positive nuclei and delocalised electrons Held together by the attraction between their positive nuclei and negatively charged shared pair of electrons Is atoms are too close, nuclei will repair each other If too fat parts, the nuclei will not attractnon-polar

Chemisty (18 decks)

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