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Higher chemistry > Chemical Changes And Structure > Flashcards

Chemical Changes And Structure Flashcards

1
Q

groups

A

vertical columns within the table which contains elements with similar chemical properties resulting from a common number of electrons in the outer shell

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2
Q

periods

A

rows of elements arranged with increasing atomic number, demonstrating an increasing number of outer electrons and a move from metallic to non-metallic characteristics

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3
Q

what are the different types of structures

A

metallic, covalent molecular, covalent network, monatomic

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4
Q

what is covalent radius

A

a measure of the size of atom

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5
Q

how can the trends in covalent radius across periods and down groups be explained in terms of

A

the number of occupied shells, and the nuclear charge

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6
Q

what is first ionisation energy

A

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

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7
Q

what are second, third, fourth etc. ionisation energies

A

the energies required to remove further moles of electrons

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8
Q

what can trends in ionisation energies across periods and down the groups be explained in terms of?

A

the atomic size, nuclear charge and the screening effect due to inner shell electrons

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9
Q

electronegativity

A

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

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10
Q

what happens in covalent bonds

A

atoms share pairs of electrons

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11
Q

what is a covalent bon a result of

A

two positive nuclei being held together by their common attraction for the shared pair of electrons

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12
Q

how are polar covalent bonds formed

A

when the attraction of the atoms for the pair of bonding electrons is different

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13
Q

what are ionic bonds

A

the electrostatic attraction between positive and negative ions

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14
Q

what do ionic compounds form

A

lattice structures of oppositely charged ions

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15
Q

what can pure covalent bonding and ionic bonding be considered as

A

opposite ends of a bonding continuum, with polar covalent lying between these two extremes

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16
Q

what happens if the difference in electronegativities between the bonded atoms is large

A

the more polar it will be and then the movement of bonding electrons from the element of lower electronegativity to the element of higher electronegativity is complete, which results in the formation of ions

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17
Q

what are the intermolecular forces acting between molecules known as

A

Van Der Waals forces

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18
Q

what are the types of intermolecular forces

A

london dispersion forces and permanent dipole-permanent dipole interactions that include hydrogen bonding

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19
Q

what are london dispersion forces

A

forces of attraction that can operate between all atoms and molecules, they are much weaker than all other types of bonding

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20
Q

how are london dispersion forces formed

A

they are formed as a result of electrostatic attraction between temporary dipoles and induced dipoles caused by the movement of electrons in atoms and molecules

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21
Q

what is the strength of london dispersion forces related to

A

the number of electrons within an atom or molecule

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22
Q

what is a molecule described as if it has a permanent dipole

A

polar

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23
Q

what atoms of what elements are there hydrogen bonds between the atoms present

A

strongly electronegative elements such as fluorine, oxygen and nitrogen, which are highly polar

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24
Q

what are hydrogen bonds

A

electrostatic forces of attraction between molecules that contain these highly polar bonds. They are stronger than other forms of permanent dipole-permanent dipole interaction but weaker than a covalent bond

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25
Q

what are differences in the boiling points and melting points of polar substances and non-polar substances with similar numbers of electrons

A

the melting points and boiling points of polar substances are higher than the boiling points and melting points of non-polar substances

26
Q

what properties of substances are affected by hydrogen bonding

A

boiling points, melting points, viscosity and solubility/miscibility in water

27
Q

what does hydrogen bonding between molecules in ice result in

A

an expanded structure that causes the density of ice to be less than that of water at low temperatures

28
Q

what do ionic compounds and polar molecules tend to be soluble in

A

polar solvents such as water

29
Q

what do ionic compounds and polar molecules tend to be insoluble in

A

non-polar solvents

30
Q

what do non-polar molecular substances tend to be soluble and insoluble in

A

soluble in non-polar solvents and insoluble in polar solvents

31
Q

where do pure covalent bonds exist between

A

atoms with the same electronegativities and the electrons are shared evenly and the molecule has no ionic character

32
Q

what are polar covalent molecules known as

A

dipoles

33
Q

when do polar covalent bonds arise

A

when atoms do not share their pair of electrons equally

34
Q

what happens during pure covalent bonding

A

atoms with higher electronegativities pull the shared pair of electrons closer

35
Q

what are london dispersion forces caused by

A

the temporary uneven distribution of electrons within atoms forming temporary dipoles

36
Q

what happens to the atom with the higher electronegativity in ionic bonds

A

it pulls the shared electrons towards itself completely forming a negative ion

37
Q

what happens to the atom with the lower electronegativity in ionic bonds

A

it loses its bonding electron to form a positive ion

38
Q

properties of ionic compounds

A

they form ionic lattices with high melting and boiling points

39
Q

why do polar substances have higher melting point and boiling points compared to non-polar substances

A

because the molecules are more difficult to seperate

40
Q

what type of attraction is found in metallic bonding

A

an electrostatic attraction between the positive metal ions and the delocalised electrons

41
Q

why are metal elements good conductors of electricity

A

because the have delocalised electrons

42
Q

what are discrete covalent molecules held together by

A

strong covalent bonds between atoms and weak intermolecular forces between molecules

43
Q

what are the covalent molecular elements

A

chlorine, fluorine, oxygen, nitrogen, hydrogen, sulfur and carbon in the form of fullerenes

44
Q

what are covalent networks held together by

A

strong covalent bonds

45
Q

what are monoatomic elements

A

stable atoms with full outer energy levels so they do not usually form molecules with other atoms

46
Q

characteristics of monatomic elements

A

low melting and boiling points because it is easy to overcome the weak intermolecular forces between the atoms

47
Q

what happens to the ionisation energy as you move across a period from left to right

A

it increases as the atoms have more protons in the nucleus so outer electrons are harder to remove

48
Q

what happens to the ionisation energy as yo move down a group

A

it decreases because the outer electrons are further away from the nucleus and shielded by the full inner shells of electrons, and are easier to remove

49
Q

what happens to the electronegativity as you move across a period from left to right

A

it increases as the atoms have more protons in their nuclei which increases their effective nuclear charge and attracting bonding electrons more strongly

50
Q

what happens to the electronegativity as you move down a group in the periodic table

A

it decreases as you have more energy levels so the nuclei are further away from the bonding electrons and shielded from it

51
Q

what is the rate of a chemical reaction proportional to

A

the concentration of reactants present

52
Q

what happens as a reaction proceeds

A

the concentration of the reactants decreases which results in a decrease in the rate of the reaction

53
Q

activation energy

A

the minimum kinetic energy required for a reaction

54
Q

why must must reactant molecules have enough energy to collide

A

so that they can overcome the repulsive forces

55
Q

activated complex

A

high energy intermediate state where bonds are breaking and forming

56
Q

what must happen in order for an activated complex to be formed

A

collision of molecules with the correct geometry

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57
Q

what are the four factors that affect how reactant molecules collide

A

temperature, concentration, particle size, catalyst

58
Q

what do catalysts do

A

they reduce the activation energy of the reaction by providing a lower energy pathway

59
Q

what affect does increasing temperature have on kinetic energy

A

the number of particles with kinetic energy above the activation energy increases

60
Q

enthalpy change

A

the difference in energy between reactants and products

61
Q

what do potential energy diagrams show

A

the progress of a reaction from reactants to products

Higher chemistry (3 decks)

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