C2- The Periodic Table

Question 1

1. How are the elements in the Periodic Table arranged?

Answer 1

• In order of atomic (proton) number

* Elements with similar properties are in columns, known as groups

Question 2

2. Why is the table known as the Periodic Table?

Answer 2

• Because similar chemical properties occur at regular intervals

Question 3

3. What do elements in the same group have in common?

Answer 3

• They have the same number of electrons, which gives them similar chemical properties.

Question 4

4. Before the discovery of protons, neutrons and electrons, how did scientists classify the elements?

Answer 4

• The elements were arranged into order of their atomic weight

Question 5

5. What were the issues with placing elements in order of atomic weight?

Answer 5

• The Periodic Table was incomplete

* Some elements were placed in groups that were inappropriate, i.e. the chemical properties were not similar.

Question 6

6. What did Dimitri Mendeleev do to overcome this problem?

Answer 6

• He left gaps for elements that had not been discovered
• He changed the order of the elements in some places
• Knowledge of isotopes made it possible to explain why the order based on atomic weight was not always correct

Question 7

7. What elements form positive ions?

Answer 7

• Metals. These are the majority of the elements and are on the left-hand side and toward the bottom of the Periodic Table

Question 8

8. What elements for negative ions?

Answer 8

• Non-metals. These are found on the right-hand side and the top of the Periodic Table

Question 9

1. What are the elements in Group 0 called?

Answer 9

• The elements in Group 0 are called the noble gases

Question 10

2. Why are the noble gases unreactive?

Answer 10

• They are unreactive and do not easily form molecules because they have stable arrangements of electrons

Question 11

3. How many electrons do noble gases have in their outer shells?

Answer 11

• They have eight electrons, except for helium which has two electrons

Question 12

4. How do the boiling points of the noble gases change going down the group?

Answer 12

• The boiling points of the noble gases increase with increasing atomic mass going down the group

Question 13

1. What are the elements in Group 1 called?

Answer 13

• The elements in Group 1 are called the alkali metals

Question 14

2. Why are the alkali metals so reactive?

Answer 14

• They have their characteristic properties as they have only one electron in their outer shell

Question 15

3. What are the products of the reaction of an alkali metal with water?

Answer 15

• When reacted with water, the alkali metal will form the corresponding metal hydroxide and hydrogen gas. The reaction is accompanied by fizzing and release of heat, which becomes increasingly violent as you go down the group.

Question 16

4. What are the products of the reaction of an alkali metal with oxygen?

Answer 16

• When burned in oxygen, the corresponding basic metal oxide is formed. Again, the reaction is more violent as you go down the group.

Question 17

5. What are the products of the reaction of an alkali metal with chlorine?

Answer 17

• When burned in chlorine, the corresponding metal chloride is formed. Again, the reaction is more violent as you go down the group.

Question 18

6. Why does reactivity increase going down the group?

Answer 18

• Reactivity increases as atomic size increases going down the group. In larger atoms, the outer electron is further away from the nucleus and less tightly held, so it is easier to remove the electron to form a positive ion.

Question 19

1. What are the elements in Group 7 called?

Answer 19

• The elements in Group 7 are called the halogens

Question 20

2. Why do the halogens all have similar reactions?

Answer 20

• They all have seven electrons in their outer shell and so have similar chemical properties

Question 21

3. What is a diatomic molecule?

Answer 21

• Pairs of atoms joined together by a covalent bond. Fluorine, chlorine, bromine and iodine exist as diatomic molecules

Question 22

4. What type of compounds are formed when the halogens react with a metal?

Answer 22

• Ionic compounds are formed, with oppositely charged ions (metal positive, halogen negative) held together by a lattice of ionic bonds

Question 23

5. What type of compounds are formed when halogens react with a non-metal?

Answer 23

• Simple molecules are formed, held together by a covalent bond.

Question 24

6. What trends are seen as you go down group 7?

Answer 24

• Size of the atoms increase, as does the relative molecular mass of the molecules
• Melting point increases
• Boiling point increases
• Reactivity decreases as a result of the reduced ability of larger atoms to attract an electron to complete its outer shell

Question 25

7. What is halogen displacement?

Answer 25

• A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt

Question 26

1. Where are the transition metals found on the Periodic Table?

Answer 26

• The transition metals occupy the central block of the Periodic Table

Question 27

2. Compared with Group 1 metals, what are the main differences in properties and reactivity?

Answer 27

• Melting points of transition metals are much higher compared to group 1 metals
• Densities of transition metals are much higher compared to group 1 metals
• Transition metals are much harder and stronger than group 1 metals, which are very soft
• Transition metals react only very slowly with water, oxygen and the halogens

Question 28

3. What are the characteristic properties of the transition metals?

Answer 28

• The have variable oxidation states (form ions with different charges, e.g. Cu+ and Cu2+)
• They tend to form compounds that are coloured
• Transition metals are useful as catalysts in many reactions