The periodic table Flashcards
Who created the modern periodic table?
Mendeleev.
How did Mendeleev’s periodic work?
By grouping elements with similar properties and order of atomic weights.
Why did Mendeleev’s periodic table work?
He left gaps for undiscovered masses and assumed they existed. These elements and their masses were later discovered and placed in the table.
In the early 20th century what happened to the periodic table with the discovery of protons and neutrons?
The table was rearranged in order of atomic numbers rather than mass numbers.
Group 1 elements are known as what?
Alkali metals.
Properties of Group 1 elements.
Low density.
Ions of +1.
Form ionic compounds.
Ionic compounds are white solids which dissolve in water.
React with water to produce hydrogen.
Form hydroxides which dissolve in water (alkali solutions).
In Group 1 the further down the group the…
…the more reactive.
…the lower its melting and boiling point.
Compared with Group 1, transition elements…
… have higher melting and boiling points (except mercury).
…have higher densities.
…are harder and stronger.
…are much less reactive.
…react less vigorously with water or oxygen.
Transition element do what?
Form differently charged ions.
What are transition element compounds often useful for?
Catalysts.
Elements in Group 7 are known as what?
Halogens.
Group 7 element ions have what charge?
-1.
The further down Group 7 the…
…less reactive the element.
…higher its melting and boiling point.
A more reactive halogen can do what to a less reactive halogen in an aqueous solution of its salt?
Displace it.
How can the trends in reactivity in groups in the periodic table be explained?
Because the higher the outer energy level of electrons the more easily electrons are lost and the harder they are to gain due to weaker electrostatic attractions within the atom.
