chapter 12 - the periodic table

Question 1

• describe the periodic table

Answer 1

a method of classifying elements and its use to predict properties of elements.

Question 2

how are elements arranged in the periodic table?

Answer 2

the are arranged according to their proton number.
thus, the elements show periodicity: elements with similar properties appear at regular intervals.
the similar elements are arranged into columns.

Question 3

what are the columns numbered I to VIII?

Answer 3

Families called groups.

Question 4

what are the rows numbered 0 to 7?

Answer 4

periods.

Question 5

what is the point of the zig-zag line?

Answer 5

it separates metals from non-metals
metals to the left (except for hydrogen)
non-metals to the right

Question 6

*describe and explain the relationship between
Group number, number of outer shell electrons
and metallic/non-metallic character

Answer 6

the group number is the same as the number of outer shell electrons in the atoms.
outer shell electrons dictate how an element behaves.
all elements in a group have similar reactions.
elements of group VIII elements have a very stable arrangement of e- —> unreactive.
groups I to III lose e- —> metals except for boron.
groups IV to VII gain e- —> non-metals.
metallic character of the elements increases as you go down a group
atoms with the same number of valency electrons react in a similar way.

Question 7

what is another name for outer-shell electrons?

and what is valency?

Answer 7

valency electrons

valency is the number of electrons atoms of an element lose, gain or share, to form a compound.

Question 8

what does the period of an element tell you?

Answer 8

the number of electron shells in the atoms.

Question 9

what are artificial elements?

Answer 9

ex) neptunium (Np), lawrencium (Lr).
they have been created in a lab.
they are radioactive, their atoms break down very quickly, that is why they aren’t found in nature.

Question 10

*describe the change from metallic to non-metallic character across a period

Answer 10

across a period there is a trend, a change from metal to non-metal.

Question 11

what are alkali metals?

Answer 11

they are the elements of group I

Question 12

what are the physical properties of alkali metals?

Answer 12

they are not typical metals:

• good conductors of heat and electricity
• softer than most metals, can be cut with a knife.
• shiny silvery surfaces when freshly cut.
• have low densities, float on water- while reacting with it.
• low melting and boiling points, compared with most metals.

Question 13

from what you’ve learnt above

*Describe lithium, sodium and potassium

Answer 13

• they are elements of Group I

- a collection of relatively soft metals showing a trend in melting point, density and reaction with water.

Question 14

*identify the trends in physical properties of group I

Answer 14

• softness increases going down the group
• density increases going down the group
• melting and boiling point decreases going down the group.

Question 15

describe the reactivity of alkali metals

Answer 15

alkali metals are the most reactive of all the metals.
1- they react vigorously with water. hydrogen bubble off, leaving solutions of their hydroxides which are alkalis.
2- when they react with chlorine, they burst into flame, burn brightly, forming chlorides.
3- the burn fiercely in oxygen to form oxides, which can dissolve in water to give alkaline solutions.

Question 16

explain why alkali metals are so reactive

Answer 16

• they need to lose only one e-, to gain a stable outer shell.
• they have a strong drive to react with other elements and compounds, in order to give up this 1 electron.
• form positive (1+) ions.
• they form ionic compounds.
• they are usually kept under oil to stop them from reacting.

Question 17

explain why alkali metals react in similar ways

Answer 17

• lithium floats and fizzes.
• sodium shoots across the water.
• potassium melts with the heat of the reaction, and the hydrogen catches fire —> burns with a lilac flame.
  they react in a similar way because they have the same number of valency electrons.

Question 18

*identify the trends in chemical properties of group I

Answer 18

• reactivity increases going down the group

Question 19

explain why reactivity of alkali metals increases going down the group

Answer 19

• As you go down Group 1, the number of shells of electrons increases by 1 (Period number increases down the Periodic table).
• This means that the outer electron is further away from the nucleus so there are weaker electrostatic forces of attraction.
• This requires less energy to overcome the electrostatic forces of attraction between the negatively charged electron and the positively charged nucleus.
• This allows the electron to be lost easily, making it more reactive as you go down the Group

Question 20

what are the halogens?

Answer 20

• elements of group VII.

all halogens form colored gases, are poisonous, form diatomic molecules.

Question 21

from what you’ve learnt above
*Describe the halogens, chlorine, bromine and
iodine

Answer 21

• elements of Group VII.

- a collection of diatomic non-metals showing a trend in color and density.

Question 22

*identify the trends in physical properties of group VII

Answer 22

F2 --> yellow gas
Cl2 --> green gas
Br2 --> red liquid 
I2 --> black solid
- color gets deeper going down the group
- density increases going down the group
- boiling point increases going down the group

Question 23

*identify the trends in chemical properties of group VII

Answer 23

• reactivity decreases going down the group

Question 24

why are halogen so reactive?

Answer 24

• their atoms need just one more e- to reach a stable outer shell.
• they have a strong drive to react with other elements or compounds, to gain this 1 e-.
• form negative (1-) ions.

Question 25

*state the reaction of halogens with other halide ions

Answer 25

a halogen will displace a less reactive halogen from a solution of its halide.
1- when chlorine water (solution of chlorine) is added to a colorless solution of potassium bromine, the solution turns orange.
Cl2 + 2KBr —> 2KCl + Br2
bromine is pushed out of its compound, it has been displaced.
2- chlorine water is added to a solution of potassium iodide, the solution turns red-brown.
Cl2 + 2KI —> 2KCl + I2
iodine has been displaced.

Question 26

what are the noble gases?

Answer 26

elements of group VIII

Question 27

• describe the noble gases

Answer 27

unreactive, monoatomic, colorless gases which occur naturally in air.

Question 28

*explain why noble gases are unreactive and monoatomic in terms of electronic structure

Answer 28

their atoms already have a stable/ full outer shell.

no need to react to gain or lose electrons.

Question 29

*identify the trends in physical properties of group VIII

Answer 29

• atoms increase in size and mass going down the group.
• density of the gases increases going down the group
• boiling points increase going down the group.

Question 30

*State the uses of the noble gases in providing an

inert atmosphere

Answer 30

1- argon in lamps:
filler in tungsten light bulbs.
protects metals from that are being welded.
2- helium for filling balloons and airships:
it is much lighter than air and will not catch fire.

Question 31

what are other uses of noble gases?

Answer 31

1- neon is used in advertising signs. (it glows red but its color can be changed by mixing it with other gases)
2- krypton is used in laser (for eye surgery) and in car headlamps.
3- xenon is used in lighthouse lamps, lights for hospital operating rooms and car headlamps. (gives a light like bright daylight but with a blue tinge)

Question 32

what are the transition elements?

Answer 32

the block of 30 elements in the middle of the periodic table.

Question 33

*describe the transition elements

Answer 33

• metals.
• have high densities
• high melting points and
• form colored compounds, which, as elements and compounds, often act as catalysts
• they have variable oxidation states.

Question 34

what are the physical properties of transition elements?

Answer 34

• hard, tough and strong.
• high melting points.
• high densities.
• malleable.
• good conductors of heat and electricity. (silver is the best conductor of electricity, copper is next)

Question 35

what are the chemical properties of transition elements?

Answer 35

• much less reactive than alkali metals (iron is an exception –> it ruts easily).
• no clear trend in reactivity, but those next to each other in the periodic table tend to be similar.
• form colored compounds.