Atomic structure and atoms

radius of nucleus

1 × 10-14

radius of atom

1 × 10-10

describe the plum pudding model

no nucleus

ball of positive charge

electrons embedded and scattered

describe the alpha particle scattering experiment

most particles went straight through (empty space)

some deflected (hit the positive nucleus)

describe the nuclear model (pre-chadwick)

mostly empty space

small positive nucleus

electrons orbit

(no nuetrons)

describe the bohr model

electrons at fixed distance from nucleus (shells)

who discovered the nuetron

chadwick

who conducted the gold foil experiment

rutherford

who discovered the shells

bohr

who proposed the plum pudding model

thompson

what are isotopes

atoms of the same element with the same number of protons and electrons and different number of nuetrons

what do atoms of the same element all have and why

same reactivity because they have the same number of electrons in the outer shell

who was the periodic table developed by

dmitri mendeleev

how did mendeleev order the atoms

by atomic weight

left gaps where no atoms fit

what did mendeleev predict

the properties of the atoms that woukd fit his gaps

properties of group 1 metals

low density

soft

how are group 1 metals stored

in oil to prevent reacting with oxygen

how do group 1 elements react with water

they fizz float and dissolve

what do group 1 produce

alkali metals

properties of group 7

toxic

colored

what happens as you go down group 7

reactivity decrease and b.p increases

what happens as you go down group 1

reactivity increases

b.p decreases

what are metal hydroxides

compounds that dissolve in water to produce alkaline solutions

how do group 1 atoms react with chlorine gas

vigorously

properties of noble gases (explain)

inert because they have a full outer shell of electrons

what is a compound

two or more different types of elements bond chemically to make a substance

what is needed to seperate compounds

a chemical reaction

what is a mixture

two or more different types of elements or compounds NOT chemically bonded together to make a substance

how do properties in making a compound differ from in a mixture

in a compound the properties are completely different from the original elements, the stay the same in a mixture (they will have a bit of each)

what is chromatography used for?

seperating substances in a mixture

what is filtration used for

to seperate an insoluble solid from a liquid reaction mixture

what is evaporation/crystillazation used for

to seperate a soluble salt from a solution.

differences in evaporation and crystallisation

evaporation is faster

you can only use it if the salt doesnt decompose when heated

what is simple distillation used for

seperating a liquid from a solution

problem with simple distillation

can only use it with elements with different boiling points

what is fractional distillation used for

to seperate a mixture of liquids

what are the shells closest to the nucleus called?

the lowest energy levels

how did mendeleev categorise elements

physical and chemical properties

atomic weight

properties of metals

strong

malleable

conductors

high bp and mp

properties of non metals

dull

brittle

insulators

low densities

properties of transition metals

dense

catalysts

coloured

strong

conductors

group 1 compared to transition metals

more reactive

less strong/hard

lower boiling point

colour of fluorine

yellow gas

colour of chlorine

green gas

colour of bromine

red liquid

colour of iodine

grey crystals/ purple vapour