periodic table

Question 1

what does the group represent?

Answer 1

valency (number of valence electrons)
—same group = same valency = similar chemical properties

Question 2

what does the period represent?

Answer 2

number of electron shells
—same period = same number of electron shells

Question 3

across a period elements change from…

Answer 3

metals to non-metals

Question 4

what are metalloids?

Answer 4

elements that have both the properties of metals & non-metals
(B, Si, As)—along the zig-zag line

Question 5

what is metallic character?

Answer 5

ease at which the atom of an element forms a positive ion through the loss of electrons
(metals have high metallic character as it is easier for them to LOSE a few electrons rather than gain many)

Question 6

does metallic character increase/decrease along the period?

Answer 6

decrease.
across a period, proton number increases while number of electron shells remain constant
= increased attraction between nucleus & valence electrons
= decrease in the ability to lose valence electrons

Question 7

does metallic character increase/decrease down the group?

Answer 7

increase.
number of electron shells increase down the group
= valence electrons are further away from the nucleus
= force of attraction between nucleus & valence electrons decrease/weaker
= ability to lose electrons increase

Question 8

what are the elements in period 3?

Answer 8

Na, Mg, Al, Si, P, S, Cl, Ar

Question 9

what are the structures of the elements in period 3?

Answer 9

Na, Mg, Al (metals):
giant metallic lattice structure

Si (metalloid):
giant covalent structure

P, S, Cl, Ar (non-metals):
simple molecular structure

Question 10

what are the type of bonding in period 3?

Answer 10

Na, Mg, Al (metals):
strong FOA between positive ions & sea of delocalised electrons

Si (metalloid):
strong covalent bonds between atoms

P, S, Cl, Ar (non-metals):
weak IMFOA between molecules (except Argon: weak interatomic forces)

Question 11

what are the variation in m.p. in period 3?

Answer 11

Na, Mg, Al (metals):
no. of valence electrons increase
= strength of electrostatic FOA increase
= m.p. increase

Si (metalloid):
giant covalent structure
= require large amount of energy to break the strong Si-Si covalent bonds
= m.p. reaches a max

S, Cl, Ar (non-metals):
simple molecular structure
= smaller molecule size
= weaker IMFOA
= little energy required to overcome weak IMFOA
= m.p. drops/is low

Question 12

what is the electrical conductivity in period 3?

Answer 12

Na, Mg, Al (metals):
no. of valence electrons increase
= no. of delocalised electrons increase
= electrical conductivity increase

Si (metalloid):
all valence electrons are involved in covalent bonding
= electrical conductivity drops sharply

P, S, Cl, Ar (non-metals):
no valence electrons available as they are all involved in covalent bonding
= electrical conductivity drops to zero

Question 13

what are elements of group 1?

Answer 13

alkali metals:
lithium, sodium, potassium, rubidium, caesium, francium
(most reactive metals)

Question 14

what are the 6 properties of group 1?

Answer 14

• soft: can be cut easily
• low density (increases down the group, except for potassium)
• low m.p. (decreases down the group)
• similar chemical properties (due to same valency)
• reducing agent
• highly reactive

Question 15

why does group 1 have low m.p.?

Answer 15

proton number is constant (due to the group) while electron shells increase (due to period)
= weaker electrostatic FOA between positive ions & sea of delocalised electrons
= less energy required to overcome weak electrostatic FOA
= low m.p.

Question 16

why does group 1 have high reactivity?

Answer 16

weak electrostatic FOA between nucleus & valence electrons
= atoms loses valence electrons more easily
= more reactive

Question 17

metal + water reaction?

Answer 17

metal + water —> metal hydroxide (alkali) + hydrogen

Question 18

group 1 metals reaction to water?

Answer 18

lithium: reacts quickly, floats on water, no flame
sodium: reacts very quickly, yellow flame
potassium: reacts violently, lilac flame
rubidium: reacts very violently, no flame

Question 19

elements in group 17?

Answer 19

fluorine, chlorine, bromine, iodine, astatine

Question 20

what are 8 properties of group 17?

Answer 20

• most reactive non-metals
• exists as diatomic covalent bonds
• form acids when bonded to hydrogen (e.g. HCl, HF, HBr)
• m.p. & b.p. increases down the group
• do not conduct electricity
• becomes darker down the group
• reactivity decreases down the group
• oxidising agent (itself reduces)

Question 21

why does the m.p. & b.p. increase down the group?

Answer 21

go down group
= molecular size increases
= IMFOA becomes stronger
= require more energy to overcome

Question 22

what is the structure of group 17?

Answer 22

simple molecular structure

Question 23

why can’t group 17 conduct electricity?

Answer 23

since halogens have simple molecular structures, all their molecules are involved in covalent bonding and hence have no mobile charge carriers (e.g. positive ions or electrons)
= neutral molecules

Question 24

why does the reactivity for group 17 decrease down the group?

Answer 24

atomic size increases (as electron shell number increase down a group)
= valence shell further away from nucleus
= electrostatic FOA between valence electrons & nucleus weaker
= ability to attract an electron decreases

Question 25

metals gain or lose electrons? non-metals gain or lose electrons?

Answer 25

metals: lose electrons (it’s easier for them to lose a few rather than gain many) non-metals: gain electrons

Question 26

order of group 17 reactivity?

Answer 26

1. fluorine 2. chlorine 3. bromine 4. iodine 5. astatine

Question 27

explain displacement in group 17?

Answer 27

more reactive displaces less reactive from halide solution halide solution: any solution that contains a halogen (normally aqueous) - it is a redox reaction as electrons are transferred from the less reactive halogen ( in its halide solution) to the more reactive halogen

Question 28

what are the elements in group 18?

Answer 28

noble gases: helium, neon, argon, krypton, xenon, radon

Question 29

what are 6 properties of group 18?

Answer 29

- inert, do not undergo reaction readily (easily) - monoatomic gases coloured & odourless gases at r.t.p. - very low m.p. & b.p. - do not conduct electricity - insoluble in water

Question 30

why are the elements in group 18 inert?

Answer 30

they have a fully-filled valence electron shell (either duplet or octet structure) & do not need to gain/lose electrons to achieve stable electronic configuration

Question 31

why doesn’t group 18 conduct electricity?

Answer 31

they have no mobile charge carriers (ions or electrons) to conduct electricity

Question 32

uses of noble gases?

Answer 32

helium: fill balloons neon: lights & advertising signs argon: fill light bulbs

Question 33

what groups are transition metals?

Answer 33

group 3-11

Question 34

colour of fluorine (Fl2) at r.t.p. & aq solution?

Answer 34

r.t.p: pale yellow gas aq solution: nil

Question 35

colour of chlorine (Cl2) at r.t.p. & aq solution?

Answer 35

r.t.p: yellow-green gas aq solution: yellow-green solution

Question 36

colour of bromine (Br2) at r.t.p. & aq solution?

Answer 36

r.t.p: red-brown liquid aq solution: red-brown solution

Question 37

colour of iodine (I2) at r.t.p. & aq solution?

Answer 37

r.t.p: purple-black liquid aq solution: brown solution

Question 38

halogen vs halide?

Answer 38

halogen: gas form (e.g. Cl2, Br2) halide (ion): natural form (e.g. Cl-, Br-)

Question 39

what are 5 properties of transition elements?

Answer 39

- high m.p. & b.p. - high densities - variable oxidation states in their compounds = can form ions with different oxidation states - form coloured compounds - make good catalysts

Question 40

what is the definition of catalysts?

Answer 40

a substance that increases the rate of a chemical reaction & remains chemically unchanged at the end of the reaction