C3.1 The periodic table

Question 1

How did Newlands and Mendeleev attempt to classify the elements?

Answer 1

by arranging them in order of their ATOMIC WEIGHTS

Question 2

In the periodic table, elements with similar properties are….

Answer 2

in the same GROUP

Question 3

Why is the periodic table called the periodic table?

Answer 3

because similar properties occur at regular intervals

Question 4

Why was Newlands criticised when attempting to classify the elements in the periodic table?

Answer 4

• as he put elements in groups that did not have similar properties
• mixed up metals and non metals
• didn’t leave gaps for elements that had not yet been found

(he placed elements in inappropriate groups because the strict order of atomic weights was followed)

Question 5

Why did Newlands end up placing some elements into the wrong groups when attempting to classify the elements?

Answer 5

As he did not leave gaps for elements that had not been found

Question 6

What did Newlands notice when attempting to classify the elements?

Answer 6

that every 8th element had similar properties, so he listed them into rows of seven

• Newlands’ Octaves

Question 7

How did Mendeleev overcome some of the problems in classifying the elements?

Answer 7

by leaving gaps for elements that he thought had not been discovered

Question 8

Why did scientists at first regard the periodic table of elements first as curiosity?

Answer 8

as at the time there was not much evidence to suggest that the elements really did fit together in that way

Question 9

When did scientists realise that the periodic table was a useful tool and an important summary of the structure of atoms?

Answer 9

After Mendeleev released his work, newly discovered elements fitted into gaps he left- convincing evidence

in 20th century- discovery of neutrons, electron , protons- provided more evidence in favour

Question 10

What happened to the order of the periodic table when protons, electron and neutrons were discovered in the 20th century?

Answer 10

the periodic table was arranged in order of (atomic numbers)

Question 11

In the periodic table, what does the group number show?

Answer 11

how many electrons are in the outer shell

Question 12

Elements in the same group have the same number of…..

Answer 12

electrons in their highest occupied energy shell

Question 13

What are the elements in group 1 called?

Answer 13

the alkali metals

Question 14

Describe some of the properties of the alkali metals

Answer 14

• low density (first 3 are less dense than water)
• react with nonmetals to form ionic compounds (in which the metal ion carries a change of +1.) The compounds are WHITE SOLIDS that DISSOLVE IN WATER to form colourless solutions
• react with water, releasing hydrogen
• form hydroxides that dissolve in water to give alkaline solutions

Question 15

What is the test for hydrogen?

Answer 15

A lighted splint will indicate hydrogen by producing a squeaky pop

Question 16

In group 1, the further down the group an element is……

Answer 16

• the more reactive the element

- the lower its melting and boiling point

Question 17

Why in group 1, the further down the group, the more reactive the element?

Answer 17

In elements further down the group, there is a greater distance between the nucleus and the outer electrons because there are more shells. This means there is a weaker attraction between the nucleus and outer electrons due to SHIELDING. This means it is easier to lose electrons.

Question 18

Compared to group 1, transition elements….

Answer 18

• have higher melting points (except for mercury)
• have higher densities
• are stronger and harder
• are much less reactive and so do not react as vigorously with water or oxygen

Question 19

Who first started to classify the element?

Answer 19

Newlands and then Mendeleev

Question 20

Many transition elements have ions with…..

Answer 20

• different charges
• form coloured compounds
• and are useful as catalysts

Question 21

What are the elements in group 7 of the periodic table called?

Answer 21

the HALOGENS

Question 22

What do elements in group 7, the halogens, react with?

Answer 22

with metals to form ionic compounds in which the halide ion carries a charge of -1 (gains an electron)

Question 23

In group 7, the further down an element is….

Answer 23

the less reactive the element

the higher its melting and boiling point

Question 24

Why in group 7, the further down the group, the less reactive the element?

Answer 24

Because it is harder to gain an electron because the outer shell is further from the nucleus

There is less attraction from the nucleus pulling electrons into the atom

Question 25

A more reactive halogen can….

Answer 25

displace a less reactive halogen from an aqueous solution of its salt

eg - chlorine can displace bromine from an aqueous solution of its salt. - chlorine + potassium bromide—-bromine + potassium chloride

Question 26

What are some properties of the halogens?

Answer 26

• nonmetals
• have coloured vapours
• All exist as molecules

Question 27

What are some differences you would see between the reactions of potassium and lithium with water?

Answer 27

with potassium

• it would dissolve faster
• move faster on the surface
• ignites

Question 28

Explain how the modern periodic table is arranged

Answer 28

elements are in order of their proton number (atomic number)

the number of shell is the number of the period

because the number of electrons in the outer shell is the number of the group, except in the case of the noble gases

Question 29

Why did Mendeleev leave gaps for undiscovered elements in his periodic table?

Answer 29

so that elements with similar properties could be placed together

Question 30

How does the boiling point of the halogens change as you go down the group?

Answer 30

increases

Question 31

Why does chlorine displace bromine from sodium bromide?

Answer 31

chlorine is more reactive than bromine