The Periodic Table Flashcards
How did Newlands and Mendeleev organise the early periodic table?
arranged them by atomic weight
can be arranged into a table so that atoms with similar properties are in the same group
What was the main problem with the early periodic table and how did Mendeleev overcome this?
the table was incomplete and some elements were placed in inappropriate to group to keep the order of atomic weight
Mendeleev left gaps for elements that had not yet been discovered
How is the modern periodic table organised?
as subatomic particles were discovered in the early 20th century, the table was arranged in order of atomic (proton) number
all elements were placed in appropriate groups
organised in accordance to electronic structure, as elements in the same group have the same number of electrons in their outer shell
What are the trends in the elements in group 1 (alkali metals)?
low density (first 3 are less dense than water)
form ionic compounds with nonmetals, ion carries a charge of +1, compounds are white solids that dissolve in water
react with water, releases hydrogen
form hydroxides that dissolve in water to form alkaline solutions
melting point decreases and reactivity increases further down the group
What are the trends of transition metals in comparison to group 1?
have higher melting points (except mercury) and higher densities
are stronger and harder than group 1 metals
much less reactive, don’t react as vigorously with water or oxygen
transition metals have ions with different charges, form coloured compounds and are useful as catalysts
What are the trends in group 7 elements (halogens)?
react with metals to form ionic compounds, halide ion carries a charge of -1
further down the group an element is less reactive and has a higher boiling point
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt
Why do trends in reactivity within groups vary?
the more easily electrons are lost
the less easily electrons are gained
