Ch2 The periodic table Flashcards
John Dalton
arranged elements in order of atomic weight
table was incomplete
Dobereiner
law of triads
groups of 3 elements had similair properties
Newlands
law of octaves
properties of every 8th element was similair
assumed all elements were found so pattern didn’t work
Mendeleev
arranged in order of atomic weights
then so that periodic pattern in properties could be seen
left gaps for undiscovered elements
could predict their properties
Periodic table now
in order of atomic number
element gaps were filled in
isotopes explained why the atomic weight order didn’t work
Group 0
noble gases
Group 0 properties
unreactive(full outer shell)
boiling point increases as you go down the group
monatomic(single-atom)
Group 1
alkali metals
5 Group 1 properties
soft low density good conductor very reactive form +1 ions
As you go down group 1…
reactivity increases
boiling point decreases
electrostatic attraction of the single outermost electron from the nucleus decreases as the distance increases, so it is lost easily
nucleus is shielded by inner electrons- less attraction
Group 7
halogen gases
4 Group 7 properties
low melting + boiling points
toxic
diatomic molecules
form -1 ions
As you go down group 7…
reactivity decreases
boiling point increases
electrostatic attraction electron to the nucleus decreases as the distance increases so it’s harder to gain an electron
nucleus is shielded by inner electrons- less attraction
Groups
The number of electrons in the outermost shell of an atom
5 Transition metals properties
good conductors hard and strong high density high mpt and bpt not reactive
