3.1 the periodic table classification of elements

Question 1

group

Answer 1

A column in the periodic table.
elements in same group have similar properties

Question 2

period

Answer 2

horizontal row in the periodic table; the period number tells you how many electron shells an element has.

Question 3

metalloid

Answer 3

An element that is located between metals and non-metals in the periodic table and shows intermediate properties between a metal and a non−metal. In the “stairs”.

Question 4

what other way can you sort elements in periodic table

Answer 4

by seeing which sublevel does its valence electrons occupy
group 1 and 2= s-level
transition metals= d block
non metals= p-level

Question 5

atomic radii

Answer 5

The distance from an atom’s nucleus to the outermost orbital of one of its electrons. Usually measured as the half-distance between the nuclei of two of the same atoms bonded together.

Question 6

effective nuclear charge

Answer 6

The net positive charge from the nucleus experienced by outer valence shell electrons once the screening effect of the core electrons has been considered.

Question 7

as we move accross a period what happens to effective nuclear charge

Answer 7

elements have a greater number of protons in the nucleus and a greater number of electrons occupying the outermost energy level. This greater number of protons and valence electrons increases the effective nuclear charge

Question 8

what happens gong down a group for atomic radii

Answer 8

increases because going down group elements have more electrns that occupy higher energy levels which are found further away from the nucleus, meaning electrostatic force of attraction of nucleus to outermost electron is weaker/ less resulting in a bigger atomic radii

Question 9

what happens going accross a period for atomic radii

Answer 9

decreases as; the electrons occupy the same energy level however there is an increase in number of protons, meanig increase in the effective nuclear charge, bigger force o fattraction from nucleus to outermost electrons decreasing atomic radii

Question 10

ionic radii

Answer 10

measure of size of ion, measured by distance between nucleus and outermost ion shell

Question 11

compare radii of atom and it positive ion

Answer 11

positive ion=loss of electrons from outermost shell
positive ion is smaller than its atom
increase attraction between nucleus and outermost electron (less hsileding) bigger effective nuclear charge
thus smaller the radii
more electrons removed the smaller the radii
less electron electron repulsion

Question 12

compare radii of atom and it negative ion

Answer 12

negative ion=gained electrons
radii is bigger than atom
gain of electrons increases electron electron repulsion
decreased attraction between the nucleus and outermost electron (decrease in effective nuclear charge)
greater number of electrons gained bigger the radii

Question 13

isoelectronic meaning

Answer 13

Molecules with the same electron configuration.

Question 14

How can we compare the sizes of species that are isolectronic?

Answer 14

use effective nuclear charge

Question 15

describe pattern seen between radius of species which are isolectornic

Answer 15

isolectronic species have same number of electrons but different number of protons
bigger number of protons= bigger the effective nuclear charge, means; stronger force of attraction from nucleus to outermost elecctrons therefore smaller radii
lower effective nuclear charge= weaker force of attraction from nucleus to outermost electron, bigger radii

Question 16

ionisation energy

Answer 16

The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.

Question 17

first ionisation energy

Answer 17

The energy required to remove one mole of the most loosely held electrons from one mole of gaseous atoms in the ground state.

Question 18

general equation for first ionisation energy

Answer 18

X(g) → X+(g) + e–

Question 19

trend and explanation of first ionisation energy down group

Answer 19

-Going down a group the first ionisation energy decreases because atomic radii increases and electrons occupy higher energy levels, Electrons in higher energy levels have a weaker attraction to the nucleus so Less energy is required to remove an electron.

Question 20

trend and explanation of first ionisation energy accros a period

Answer 20

Going across a period the first ionisation energy increases, nuclear charge increases (there are more protons in the nucleus).
so the atomic radius decreases (atoms get smaller except for Ar which increases slightly compared to Cl).
More energy is required to remove an electron.

Question 21

what is the only exception in atomic radii moving accross a period

Answer 21

atomic radii gets smaller accros a period except for argon which is slightly bigger compared to chlorine

Question 22

electron affinity

Answer 22

The amount of energy released when a neutral atom gains an electron to form a negatively charged ion. in the gaseous state

Question 23

general equation for electron affinity

Answer 23

X(g) + e– → X-(g)

Question 24

first electron affinity

Answer 24

The release of energy that occurs when a neutral, gaseous atom gains one electron.
exothermic

Question 25

general trend in electron affinity going down group

Answer 25

decreases down the group further down the group elements have larger atomic radii valence shell further away from the nucleus so weaker attraction between the nucleus and outer shell electrons

Question 26

general trend in electron affinity going across the period

Answer 26

increases, elements across the period have a higher effective nuclear charge, stronger attraction between the nucleus and valence electrons.

Question 27

why do some elements do not have an electron affinity value

Answer 27

because many elements have complete filled subshells, do not tend to gain electrons

Question 28

greater the electron affinity...

Answer 28

the greater is the attraction of the ion for the electron

Question 29

electronegativity

Answer 29

A measure of how much an atomic nucleus attracts the shared electrons that are involved in a covalent bond.

Question 30

general trend in electronegativity going down the group

Answer 30

decrease down group atomic radius increases down the group from additional levels weaker attraction between the nucleus and the shared pair of electrons

Question 31

general trend in electronegativity across a period

Answer 31

increase across a period effective nuclear charge increases going across a period stronger attraction between the nucleus and the shared pair of electrons

Question 32

nobel gases relationship with electronegativity

Answer 32

do not have assigned electronegativity as they do not form shared pair of electrons with other atoms

Question 33

what are the general (all) trends down a group

Answer 33

atomic radius increases ionisation energy decreases electron affinity decreases electronegativity decreases

Question 34

what are the general (all) trends across a period

Answer 34

atomic radius decrease ionisation energy increase electronegativity increase electron affinity increases

Question 35

metallic character

Answer 35

The tendency of an element to lose electrons to form positive ions.

Question 36

what affects the metallic character

Answer 36

The lower the ionisation energy, the greater the tendency that element has for electron loss and therefore the greater metallic character.

Question 37

non metallic character

Answer 37

The tendency of an element to gain electrons to form negative ions.

Question 38

what affects the non metallic character

Answer 38

The higher the electron affinity, the greater the tendency that element has for electron gain and therefore the greater non-metallic character.

Question 39

what happens when a group 1 metal reacts with water

Answer 39

produces the metal hydroxide (ionic compound) which is soluble in water, aqueos stateand hydrogen gas

Question 40

general trend going down the group 1of reactivity with water and explanation

Answer 40

Increasing reactivity going down group 1, because elements have lower first ionisation energies due to the presence of an additional energy level, so its Easier for elements with lower ionisation energy to transfer the outer valence electron to water thus increasing reactivity with water.

Question 41

displacement reaction

Answer 41

A reaction where a less reactive element is removed from a compound by a more reactive element.

Question 42

describe what happens in terms of electrons in a displacement reaction

Answer 42

eg. Cl2(aq) + 2KBr(aq) → Br2(aq) + 2KCl(aq) the extra electron that Br- has is transferred to halogen cl2 to form Cl- ion, results in each halogen atom in Cl2 gaining an electron and each Br- loosing an electron to form Br2

Question 43

spectator ion

Answer 43

Aqueous ions that remain unchanged throughout a chemical reaction.

Question 44

what determines whether a displacement reaction will take place

Answer 44

electron affinity, if halogen has a bigger electron affinity than non metal in ionic compound it will gain the electrons lost by the metal ion and form an ionic compound instead.

Question 45

general trend for reactivity of halogens with halide ions down the group

Answer 45

down the group the number of occupied energy level sincreases meaning there is a weaker attraction between the nucleus and the valence electron/ shared pair of electrons so there is a decrease in electron affinity down the group, meaning reactivity decreases down the group

Question 46

describe the strucutre of metals and non metal

Answer 46

metals= metallic lattice giant covalent= covalent network lattice eg. silicon non metals= covalent molecule

Question 47

describe the strucutre of metals and non metal oxides

Answer 47

metals + oxygen= ionic lattice covalent netwrok lattice (giant covalent) + oxygen= covalent network lattice non metals + oxygen= covalent molecules

Question 48

what is the continuum of acid and bases in period 3

Answer 48

metal oxides= basic some transition metals are amphoteric non metal oxdies= acidic

Question 49

amphoteric

Answer 49

A substance that behaves both as an acid or a base.

Question 50

reaction between basic oxides and water

Answer 50

basic oxides= metal oxides when react with water metal hydroxide is formed which is a base

Question 51

reaction between acidic oxides and water

Answer 51

produce acids

Question 52

oxidation state

Answer 52

A number assigned to an element showing the number of electrons lost or gained (or even shared) in a compound or ion. based in electronegativites of elements

Question 53

whats the oxidation state of a pure element and why

Answer 53

0 because distribution of electrons between atoms is the same for atoms of the same element atoms in same elemnt have same tendency to gain or lose electrons thus 0 indicates no electron transfer

Question 54

oxidation state of monoatomic ions

Answer 54

eg. Cu2+ have oxidation state= to charge of ion eg. Cu= +2

Question 55

rule for oxidation state in a neutral compound

Answer 55

neutral cmpound= ionic compound, molecular etc. oxidation states must some up to 0

Question 56

rule for assigning oxidation states with metallic and non metallic charcters

Answer 56

assgin oxidation state of most metallic first= always positive then most non metallic= always negative and then assign the oxidation state for the transition metal/ element which you are unsure of character

Question 57

why is there a discontinuity for first ionisation energy between boron to beriliium

Answer 57

in practice, ionisation energy is supposed to ncrease accross a period thus from boron- beryllium, however, beryllium has its outer shell electron in a different sub level boron= s sub level beryllium= p sub level due to this the effective nuclear charge from the nucleus to the outer shell electron is smaller, as the outer electron is further away from the nucleus, an p sub orbital are slightly higher in energy and this means the first ionization energy decreases

Question 58

why is there a discontinuity for first ionisation energy between nitrogen to oxygen

Answer 58

oxygen has a lower ionisation energy than nitrogen, even though trend for first ionisation energy is supposed to increase accross a period. this is because nitrogen in the p suborbital all electrons go in singly, while in oxygen one of them goes in as a pair. This means there ia a bigger elecron electron repulsion and thus an electron is removed with more ease from the atom, therefore first ionisation energy is lower

Question 59

what is a transition element

Answer 59

elements with unfilled d suborbital, presenting specific characteristics due to this exhbiti transitional behaviour

Question 60

zinc

Answer 60

zinc is not considered a transition metal because it has filled d suborbital and thus doesnt display specific proeprties transition metals do

Question 61

transition elements and oxidation states

Answer 61

have variable oxidation state since they have valence electrons occupying both s and d suborbital, and energy difference between these suborbitals are so small, they can lose elecctrons from either orbital loss of electrons occurs from d after s

Question 62

transition elements and high melting points

Answer 62

since transition metals have vairbale oxidation states, leads to high number of valence electrons surrounding the cations in metallic lattice increased charge with increased number of valence electrons increases strength of metallic bond, recquire more energy to break thus higher melting point

Question 63

transition metals and magnetic properties

Answer 63

when elements have sublevels with unpaired electrons magnetism can be observed since transition metals have unfilled d suborbitals they experience magnetism bigger number of unpaired electrons= stronger magnetism

Question 64

transition metals and catalytic properties

Answer 64

as transition metaals have vriable oxidation states, they act as a surface for the reaction to take place where the ions can lose or gain electrons, the transition metal can either increase oxidation state of reactant or return a reactant to its original oxidation state (can either reduce or oxidise a reactant)

Question 65

catalyst

Answer 65

A substance that changes the rate of a reaction and is not used up. Although it speeds up a reaction, the catalyst itself is not changed by the reaction.

Question 66

transition metals and formation of coloured compounds

Answer 66

transition elemtns form coloured compounds, colors vary due to variable oxidation states

Question 67

transition elemtns and formation of complex ions

Answer 67

transition elemtns form complex ions, they are in center of complex ion, and they form coordination bonds with the other molecules being attracted/ ligands being attracted to it

Question 68

coordination bonds

Answer 68

A covalent bond where both of the electrons being shared in the bond have been donated by one atom.

Question 69

complex ion

Answer 69

An ion that has one or more species (ligands) bonded to a central metal ion through a coordinate covalent bond.

Question 70

what species can act as a ligand

Answer 70

one which has at least one pair of valence electrons

Question 71

how do you write a complex ion

Answer 71

square brackets around the complex ion, with round brackets inside surrounding ligand

Question 72

coordination number

Answer 72

the number of ligand surrounding a central metal ion

Question 73

successive ionisation eneryg

Answer 73

The process of removing successive electrons from an atom or positive ion.

Question 74

why are the successsive ionisation energies of transition metals lower than that of metals in group 1 and 2

Answer 74

this is because, transition metals contain electrons in the 3d sublevel while other metals do not. The 4s and 3d suborbitals are close in energy, electrons from both these sublevels can act as valence electrons, electrons are first lost from the 4s but without much more enrgy can easily be removed from the 3d, thats why they have variable oxidation states

Question 75

why do the majority of transition metals have +2 value

Answer 75

because they can easily lose electrons from the 4s sublevel

Question 76

why are transition metals colored

Answer 76

formed from transition metal ions having incomplete 3d sublevel when ligand attached to metal ion, 3d sublevel consisting of 5 orbitals splits to from slightly different energy levels some electrons occupying lower level d obritals absorb energy from visible and ultraviolet radiation and are excited into higher levels forming an excited state= d-d transitions

Question 77

what determines what colour transition metals are

Answer 77

essentially the stronger the ligand the bigger the split in d orbitals, this means the bigger the oxidation of transition metal the smaller the split bigger gaps abrosb violet wave light and their electrons are excited to a higher energy level, smaller gaps absorb red light medium= organe/ green the substance will then reflect complementary colour of what it absorbed

Question 78

general trend of melting and boiling point

Answer 78

metals in group 1,2,3 have metalllic bond, strong bond, which increases with bigger charge since more electrons in the sea of delocolised electros and bigger attraction with positive ions giant covalent strucutres have really strong bonds have a higher melting point than some metals non metals have simple covalent bonding, intermoleculear force is weak (only london forces) bigger number of electrons and bigger atomic radii the bigger chance of induced forces thus bigger melting ppoint noble gases are monoatomic have only weak londn forces of attraction

Question 79

melting point trend down group 1

Answer 79

low melting points, since they only have one outer electron to contribute to metallic bonding melting point decreases down group as atomic radii increases and attraction of nucleus for electron in metallic bond decreases

Question 80

melting point trend in group2

Answer 80

since they contribute with 2 electrons to metallic bonding, bond is stronger hence melting pint is higher, melting point decreases down group as atomic radii increases and attraction of nucleus for electron in metallic bond decreases

Question 81

non. metals group 5,6,7 trend in melting point

Answer 81

simple covalent molecules, even though bonds between the atoms in the molecle are strong and the attraction between the molecules is weak and hence meltingpoint is very low

Question 82

group 0 noble gases trend melting point

Answer 82

have full outer shell and so do not bond with each other, they monoatomic, very weak intermolecular attraction, thus very low melting point

Question 83

explain the increase in melting point from sodium to aluminium

Answer 83

aluminium has a bigger charge of 3+ while sodium has charge of 1+, bigger charge, more electrons contribute to sea if delocolised electrons there is a bigger attraction between the positive ions and the delocolised electrons, stronger metallic bond

Question 84

explain why S8 has a higher melting point than P4

Answer 84

S8 has more atoms in a molecule/ alotrope than p4 , bigger surface area, large molecules produce greater quantity/ frequency of weak london forces, making harder to break the bond

Question 85

why does silicon has highest melting point and argon has lowest melting point

Answer 85

silicon has a giant covalent bonds while argon is simple monoatomic molecule with weak london forces

Question 86

group 1 trends going down group

Answer 86

more soft more reactive lower ionisation energies

Question 87

why does softness increase going down group 1

Answer 87

as you go down group 1 there is an increase in sublevels, this means that valnce electrons get further away from the nucleus, there is a weaker electrostatic force of attraction, less force is recquired to break metallic bond thus metals get softer and melting point decreases

Question 88

explain trend in melting point in group 7- halogens

Answer 88

halogens are diatomic simple covalent molecules so the intermolecular force is only weak london dispersion force, so low melting point the melting point increases down the group as size of molecule increases and hence the strength of the london dispersion forces

Question 89

explain trend in reactivity group 7-halogens

Answer 89

reactivity decreases down group as added electron goes into a principle energy level further from the nucleus (decreasing electronegativity down the group). this also means than down the group, elements become weaker oxidising agents

Question 90

explain the reaction between chlorine and potassium iodide

Answer 90

chlorine is a more powerful oxidizing agent(its more electronegative) then iodine, it will oxidise iodide into iodine and reduce itself from chlorine to chloride becoming potassium chloride

Question 91

oxidation

Answer 91

loss of electrons

Question 92

reduction

Answer 92

gain of electrons

Question 93

explain trend in electrical conductivity accross a period

Answer 93

decreases as metals have sea of delocolised electrons and thus can easily conduct while ionic compounds have ions which when moleten or aqueos ions are free, however covalent lattces have no ions and even as moleten dont conduct

Question 94

why does scandium not form oxidation state with +2

Answer 94

because if it were to lose only 2 electrons it would have only one electron in the 3d suborbital, which is extremelly unstable

Question 95

why does vanadium chromium and manganses have such variable oxidation states

Answer 95

they have extremelly low ionization energies meaning that electrons can be lost easily from sub level and form stable ions

Question 96

why do transition metals commonly found in +2 oxidation state

Answer 96

because of the relatively low ionisation energy recquired to remove electrons from the s suborbital, they thus lose whole 4s subrobital instead of 3d which is much more stable

Question 97

4 examples of ligands

Answer 97

water= aqua H2o chloride= chloro negative charge Cl- ammonia= ammine NH3 cyani= cyan CN-

Question 98

how do you name complex ions

Answer 98

1. number of ligands eg. hexa= 6, tetra=4, di=2 2.name of ligand eg. aqua, chloro, ammine, cyan 3.name of centre ion and roman number oxidation state 4.ion eg. Hexaaquairon(III) ion

Question 99

whats the name of molecule arrangement with 6 ligands 4 ligand, 2 ligands

Answer 99

octahedral arrangement tetrahedral arrangement linear arrangement