C3.1 The periodic table Flashcards
Who was the first to arrange a periodic table?
Newlands
Why was Newlands’ work ignored?
Because he left no gaps for undiscovered elements
Who was the second person to arrange the elements into a periodic table?
Mendeleev
How did Mendeleev arrange his periodic table?
He put the elements in order of atomic mass, but he left gaps in order to keep the elements with similar properties in the same vertical columns (groups)
What did the gaps in Mendeleev’s table predict?
The properties of the undiscovered elements
Elements with the same properties were in the same…
Columns, known as groups
Why is it called the periodic table?
Because similar properties occur at regular intervals
In the early periodic table some elements were placed in inappropriate groups because…
Newlands did not leave gaps in his table for undiscovered elements
What was discovered in the 20th century that caused a change in the arrangement of the periodic table?
Protons, neutrons and electrons
How was the periodic table rearranged after this discovery?
The periodic table was rearranged in order of atomic (proton) numbers. Then all the elements were placed in the appropriate groups
How else can the modern periodic table be seen as arranged by?
The electronic structures of the elements, elements in the same group have the same number of electrons in their outer shell
What is the number of each group also equal to?
The number of electrons in their outer shell
What are the elements in Group 1 known as?
The alkali metals
Alkali metals have a low…
Density
Alkali metals react with non-metals to form…
Ionic compounds in which the metal ion carries a charge of +1
What ionic compounds are formed from alkali metals and non-metals?
White solids that dissolve in water to form a colourless solution
When alkali metals react with water they…
Release hydrogen
Alkali metals form…
Hydroxides that dissolve in water to give alkaline solutions
In Group 1, the further down the group an element is, the more…
Reactive it is
In Group 1, the further down the group an element is, the lower…
Its melting and boiling point
Why, in Group 1, are the elements further down more reactive?
Because they are much bigger, therefore meaning the outer shell is much further from the nucleus. This means the forces of attraction holding them together are much weaker, allowing the outer electron to be lost easily
Compared with elements in Group 1, transition elements have higher…
Melting and boiling points and higher densities
Compared with elements in Group 1, the transition elements are…
Stronger and harder
Compared with elements in Group 1, the transition elements are much less…
Reactive and therefore do not react as vigorously with water or oxygen
What do many transition elements form?
Colourful compounds
Many transition elements have ions…
With different charges
What are many transition elements useful as?
Catalysts
What are the elements of Group 7 known as?
The halogens
What do the halogens react with metals to form?
Ionic compounds in which the halide ion carries a -1 charge
In Group 7, the further down the group an element is, the less
Reactive the element is
In Group 7, the further down the group an element is, the higher…
Its melting and boiling point
Why in Group 7, are the elements further down the group less reactive?
Because the elements further down are bigger and the outer shell further away from the nucleus the forces of attraction pulling towards the nucleus are weaker, making it more difficult to gain an electron
What can a more reactive halogen do to a less reactive halogen?
A more reactive halogen can displace a less reactive halogen form an aqueous solution of its salt
What can the trends in reactivity within the groups be explained by?
The higher the energy level, the further out the outer shell is from the nucleus, the more easily electrons are lost and the less easily electrons are gained
