periodic table and history of atom

Question 1

what was JJ Thomson’s model of the atom

Answer 1

plum pudding model - ball of positive charge with negative electrons embedded in it

Question 2

what was alpha particle experiment

Answer 2

positive alpha particles fired at thin piece of gold - most went through but some were deflected - suggested the positive charge of an atom is confined in a small volume (nucleus)

Question 3

how did Bohr adapt the nuclear model

Answer 3

suggested electrons orbit nucleus at specific distances

Question 4

how did James Chadwick adapt the atom

Answer 4

suggested the nucleus also contained neutral particles

Question 5

what is group 0 and properties

Answer 5

nobles gases - chemically inert, as have stable electron configs (full outer shells), low density, non-flammable, generally low boiling point which increases down the group (as the atoms become larger so IMF become stronger, more energy is needed to overcome them), exist as single atoms

Question 6

what is group 1 and properties

Answer 6

alkali metals - low density, very reactive (1 valence electron), react with non-metals to form ionic compounds, form compounds that are white solids, dissolve in water to form colourless solutions, become more reactive down group (out shell further away from nucleus - weaker attraction

Question 7

what is group 7 and properties

Answer 7

halogens - non-metals, diatomic molecules, react with metals to form ionic compounds, form molecular compounds with other non-metals, form hydrogen halides, less reactive going down group (outer shell is further from nucleus - electron gained less easily), melting and boiling points increase going down (as the atoms become larger so IMF become stronger, more energy is needed to overcome them)

Question 8

properties of transition metals

Answer 8

good conductors of heat and electricity, can be hammered or bent into shape easily, high melting points (but mercury is a liquid at room temperature), usually hard and tough, high densities

Question 9

Gallium was discovered six years after Mendeleev published his periodic table. Give two reasons why the discovery of gallium helped Mendeleev’s periodic table to
become accepted.

Answer 9

it fitted in a gap Mendeleev had left and its properties were predicted correctly by
Mendeleev