C3 Periodic table etc

Question 1

In what order were the elements put in the early periodic table?

Answer 1

In order of increasing atomic weight. (now we call it atomic mass)

Question 2

Write an ionic equation for the reaction of the alkali metal atom

Answer 2

Li → Li⁺ + e^-

Na → Na⁺ + e^-

K → K⁺ + e^-

Rb → Rb⁺ + e^-

Cs → Cs⁺ + e^-

Question 3

How were the elements put into columns or groups?

Answer 3

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

Question 4

Why was this known as a periodic table?

Answer 4

Periodic means repeats regularly, similar properties occur at regular intervals.

Question 5

What were Newlands’ octaves?

Answer 5

John Newlands published a table showing that every eighth element had similar properties and could be grouped together.

Question 6

State the two main problems with the early periodic tables.

Answer 6

They were incomplete, only 56 elements had been found by 1865 for Newlands to octave.The elements were arranged by mass or weight which meant that some atoms did not fit the pattern and were put in the wrong groups.

Question 7

How did Mendeleev overcome problems with the early periodic tables?

Answer 7

When he made his table, Mendeleev left spaces for elements that were yet to be discovered, famously Ga and Ge, so that the other elements fitted into the right groups.

Question 8

What did Mendeleev use to sort the elements into groups in his periodic table in 1869?

Answer 8

The elements were still in order of atomic weight. They were put into groups using their properties and the formulae of their compounds.

Question 9

Explain why scientists thought the periodic table of the elements was a curiosity at first?

Answer 9

The early tables were incomplete, some only worked for the first few elements.

Question 10

What discovery led to the modern versions of the periodic table?

Answer 10

The discovery of electrons, protons and neutrons early in the twentieth century.

Question 11

In what order were the elements put in the modern periodic table?

Answer 11

In order of increasing atomic number.

Question 12

What difference did this make to the modern periodic table?

Answer 12

The elements were placed in the proper groups.

Question 13

How does this change to the order of the elements link to atomic structure?

Answer 13

The periodic table could be used to work out the electronic structure of the elements as well as the number of protons and neutrons.

Question 14

How does the electronic structure change across each period in the table?

Answer 14

In period 1 the first shell is filled, in the second period the second shell is filled, etc. e.g. Li- 2.1, Be- 2.2, B- 2.3, C- 2.4.

Question 15

How does the electronic structure change down each group in the table?

Answer 15

Elements in the same group have the same number of electrons in their highest occupied electron shell (outer shell).

Question 16

What are the electronic structures of the group 2 metals Be, Mg, Ca?

Answer 16

Be – 2.2 Mg – 2.8.2 Ca – 2.8.8.2 All of the Group 2 metals have two electrons in their outer shells

Question 17

What information tells you the number of electrons in the outer shell of an element?

Answer 17

The group number. All the Group 1 elements have one electron in their outer shell, all the group 2 elements have 2, etc.

Question 18

How many electrons does iodine have in total and how many electrons are there in the outer shell?

Answer 18

Iodine has atomic number 53 so it has 53 electrons in total. It is in group 7 so iodine has seven electrons in its outer shell.

Question 19

Describe the density of the alkali metals, be specific about the first three?

Answer 19

The alkali metals have low density, the first three (Li, Na, K) all float on water

Question 20

How do the alkali metals react with non-metals?

Answer 20

They react with non-metals to form ionic compounds in which the metal ion carries a charge of +1.

Question 21

Describe the compounds of the alkali metals with non-metals.

Answer 21

The compounds are white ionic solids that dissolve in water to form colourless solutions

Question 22

Describe the reaction of the Lithium with water

Answer 22

Lithium floats and fizzes with water, releasing hydrogen gas. It forms lithium hydroxide which dissolves in water to give an alkaline solution that turns UI indicator purple.

Question 23

Describe the pattern of the reaction of the alkali metals with water

Answer 23

The further down group 1 an element is the more reactive the element; Sodium floats, fizzes and melts. Potassium floats, fizzes, melts and catches fire (lilac fame)

Question 24

Using M as the alkali metal atom, write an equation for the reaction of an alkali metal with water

Answer 24

2M_(s) + 2H₂O_(l) → 2MOH_(aq) + H_2(g)

Question 25

Explain the pattern in reactivity going down the alkali metals.

Answer 25

As you go down the group the atoms get more shells and the single electron in the outer shell is further from the nucleus, so it is less tightly held and more easily lost. The elements need less activation energy to react i.e. they get more reactive

Question 26

What is the pattern in melting points and boiling points, going down the alkali metals?

Answer 26

The further down the group an element is the lower its melting point and boiling point.

Question 27

Compare the physical properties of the transition metals with the alkali metals.

Answer 27

Compared with the elements in Gp 1, transition elements have higher melting points (except for mercury) and higher densities. They are stronger and harder.

Question 28

Compare the chemical properties of the transition metals with the alkali metals.

Answer 28

Compared with the elements in Gp 1, transition elements are much less reactive and so do not react as vigorously with water or oxygen.

Question 29

Give the three characteristic properties of transition metals.

Answer 29

Many transition elements have ions with different charges; form coloured compounds and are useful as catalysts.

Question 30

What is the collective name for the group 7 elements?

Answer 30

They are known as the halogens.

Question 31

What happens when a group 7 element to form an ion?

Answer 31

The halogen atom becomes a halide ion. E.g. iodine atoms become iodide ions.

Question 32

How do the group 7 elements react with metals?

Answer 32

They react to form ionic compounds in which the halide ion carries a charge of –1.

Question 33

Write an ionic equation for the reaction of the halogen atom

Answer 33

F + e**^-** → F**^-** Cl + e**^-** → Cl**^-** Br + e**^-** → Br**^-** I + e**^-** → I**^-** At + e**^-** → At**^-**

Question 34

Describe the trend in colour and state going down group 7

Answer 34

The halogens get denser and the colours get more intense. F₂ is a yellow gas, Cl₂ is a green gas, Br₂ is an orange liquid, I₂ is a deep purple solid.

Question 35

Describe the trend in melting point and boiling point going down group 7

Answer 35

In Group 7, the further down the group an element is the higher its melting point and boiling point.

Question 36

What is the rule for displacement reactions of the halogens?

Answer 36

A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt. Chlorine water displaces bromine from bromide solutions.

Question 37

Give a symbol equation for displacement reactions of the halogens

Answer 37

Cl_2(aq) + 2KBr_(aq) → 2KCl(aq) + Br_2(aq) Cl_2(aq) + 2KI_(aq) → 2KCl_(aq) + I_2(aq)

Question 38

What is the trend in reactivity in group 7?

Answer 38

In Group 7, the further down the group an element is the less reactive the element

Question 39

Explain the trend in reactivity in group 7?

Answer 39

The trend in reactivity in gp 7 can be explained because the higher the energy level of the outer electrons the less easily electrons are gained. OR the gp 7 elements react by gaining/stealing electrons; in smaller atoms the nucleus is more effective at stealing electrons.