C2 The Periodic Table Flashcards
John Dalton’s periodic table
(1808) 20 elements arranged by atomic weight
John Newland’s periodic table
(1864) grouped by octaves -arranged by atomic weight. He left no gaps and the pattern broke down.
Dmitri Mendeleev’s periodic table
(1869) arranged by atomic mass but also by reactivity-he left gaps for undiscovered elements. Validity was confirmed when these gaps where filled in.
Modern periodic table
Arranged by atomic number
Why are the noble gases in Group 0 unreactive?
They have stable electron arrangements
Reactivity of Group 1 alkali metals
Increases as you go down the group
Melting and boiling points of Group 1 alkali metals
Decrease going down the group
sodium + water →
sodium hydroxide + hydrogen
Properties of Group 1 elements
low density, soft, silvery shiny surface when first cut but then goes dull as the metal reacts with the oxygen in the air
Displacement reactions between halogens
A more reactive halogen will displace a less reactive halogen from solutions of its salts
Reactivity of the Group 7 halogens
Decreases going down the group
Electrostatic attraction depends on…
The distance between the outermost electrons and the nucleus, the number of occupied inner shells of electrons, which provide a shielding effect
Physcial properties of transition elements
Good electrical and thermal conductors, hard and strong, high densities and high melting points (with the exception of mercury)
Why does the name of a compound containing a transition element usually include a Roman number?
Transition elements can form more than one ion. For example, iron may exist as Fe^2+ or Fe^3+
What are transition elements used for?
Very important in the chemical industry as catalsysts
