Group 1 - Topic 6

Question 1

Explain why some elements can be classified as alkali metals (group 1), halogens (group 7), or noble gases (group 0), based on their position in the periodic table:

Answer 1

Groups (columns) in the periodic table can be classified in specific groups as e.g. alkali metals, halogens or noble gases, because they have the same number of electrons in their outer shell (position in the periodic table determines this), therefore they have the same chemical properties

Question 2

What is the hardness of Group 1 metals like?

Answer 2

• soft
• hardness of metals decreases as you go down Group 1
• lithium cut with a sharp knife, sodium is easy to cut and potassium is like cutting butter

Question 3

What is the density of Group 1 metals like and do any elements float?

Answer 3

• density of metals generally increases as you go down Group 1 (exception is potassium)
• lithium, sodium and potassium float < 1g/cm3
• lower density than transition metals

Question 4

What is the melting and boiling points of Group 1 metals like?

Answer 4

• have relatively low melting points compared to other metals e.g. transition metals, like iron, have mp’s/bp’s in the 100s degrees C and 1000s degrees C
• the melting and boiling points of Group 1 elements decrease as you go down Group 1 - as the strength of the metallic bonds between atoms decreases

Question 5

Describe the reactivity of Group 1 metals:

Answer 5

• all elements(members) of Group 1 are very reactive and they have to be stored in oil to protect them from reacting with the oxygen in the air
• reactivity of Group 1 metals increases as you go down the Group 1

Question 6

Why are Group 1 metals stored in oil?

Answer 6

• are very reactive so stored in oil to sop them from reacting with the oxygen (O2/H2O) in the air

Question 7

What do you see when a fresh piece of Group 1 metal is cut?

Answer 7

first see a shiny surface when cut however it quickly tarnishes due to oxygen forming on the surface

Question 8

Metal + water —>

Answer 8

Metal + water —> metal hydroxide + hydrogen

Question 9

How does lithium react with water?

Answer 9

• fizzes steadily
• floats, moves on surface

Question 10

How does sodium react with water?

Answer 10

• melts into a ball then fizzes quickly
• sparks yellow

Question 11

How does potassium react with water?

Answer 11

• fizzes, melts
• gives off sparks and hydrogen burns with a lilac flame

Question 12

How does rubidium react with water?

Answer 12

• very rapid reaction

Question 13

How does caesium react with water?

Answer 13

explosion

Question 14

How do Group 1 metals react with water?

Answer 14

• Group 1 metals react vigorously with water to create an alkaline metal hydroxide and hydrogen
• fizzing
• moves around surface
• floats
• spits, flares or flame
• sodium and potassium melt

Question 15

What is the nature of the solution left behind when a Group 1 metal reacts with water?

Answer 15

• very alkaline pH 13/14
• the hydroxide formed in this reaction is what’s causing this pH change

Question 16

What gas is given off when a Group 1 metal reacts with water?

Answer 16

Hydrogen - H2

Question 17

How does the reactivity of Group 1 metals change as you go down Group 1?

Answer 17

• reactivity of Group 1 metals increases as you go down the group

Question 18

How does caesium’s reaction with water differ from lithium’s (both Group 1 metals) reaction with water?

Answer 18

• has a more explosive reaction as it’s more reactive than Li as it is further down Group 1
• extremely vigorous

Question 19

What are all the common properties of Group 1 compounds?

Answer 19

1. All Group 1 compounds are ionic
2. All Group 1 compounds are white
3. All Group 1 compounds are soluble
4. All Group 1 compound solutions are colourless

Question 20

Explain the pattern of reactivity in Group 1 metals in terms of electronic configuration:

Answer 20

• When group 1 metals react they lose an electron to form a positive ion, which now has a full outer shell, like a noble gas
• The nearer the outer shell electron(s) is to the nucleus the more difficult it is for the atom to lose the electrons to react as there is a stronger force of attraction between the positively charged nucleus and negatively charge electrons which are closer together
• Down the group – easier to lose electrons and form positive metal ions (cations) (these are formed when metals react)
• It is easier to lose electrons due to the increase in electron shells as you go down the group
• This means as the atoms are larger there is more electron shielding and the outer electron gets further from the nucleus so there is a decrease in attraction between the positively charged nucleus and the negatively charged outer shell electrons, therefore they electrons can be lost more easily which is why the metals are more reactive further down Group 1

Question 21

What colour solutions do all group 1/2 salts/compounds form?

Answer 21

colourless solutions

Question 22

Method on how to safely find reactivity of group 1 metals in classroom setting:

Answer 22

• use a trough/large container of water
• the teacher should wear safety goggles and gloves
• there should be a safety screen between the experiment and the students
• remove the metal from the container using tongs
• remove the oil and cut a small piece of the metal
• add the metal with tongs/tweezers to the water
• make sure that the class are stood well back and are wearing goggles
• repeat experiment using the same volume of water in the trough
• the metal with the most vigorous effervescence and fastest movement is the most reactive
• the metal with the least vigorous effervescence and slowest movement is the least reactive
• order the metals in terms of reactivity

Question 23

How do you make the reactions less vigorous when finding the reactivity of group 1 metals?

Answer 23

• cut a smaller pice of the metal that is getting reacted with water/oxygen then a smaller volume of sodium is being reacted with so there is a smaller and slower reaction
• use a larger container/trough of water so as there is more water more heat from the reaction is absorbed