Chemistry 3A Flashcards
what was the only 2 ways to categorise elements in the early 1800’s?
physical/chemical properties
relative atomic mass
how were the elements first ordered?
by their atomic mass
whos ‘periodic table’ is regarded as the first decent attempt?
Newlands
When did Newlands do his periodic table?
1864
how did Newlands arrange his elements?
in rows of 7
Newlands noticed that every eighth element had similar properties. What did this become known as?
Newlands law of octaves
when did the law of octaves break down and why?
on the third row due to transition metals like titanium and iron messing it up
why did the transition metals mess up the law of octaves?
because Newlands hadnt left any gaps for undiscoverd elements
for what 3 reasons did Newlands’ work get rejected by the ‘Chemical Society’ in 1865?
his groups contained elements with no similar properties (e.g. carbon and titanium)
he mixed up metals and non metals
he didnt leave any gaps for elements that had not been discovered by then
who is credited with the modern periodic table?
Dmitri Mendeleev
what did Mendeleev do different to Newlands?
left gaps for undiscovered elements, in which he predicted the properties of these elements (and he was right)
he arranged them also by atomic mass, but in order to keep the properties the same with other elements it its column (group) he left gaps
when did scientists discover protons, neutrons and electrons?
late 19th century
how is the modern day periodic table arranged?
atomic number (no. of electrons)
what corresponds the group number and the electrons of an element?
the group number=number of electrons in the outer shell
what does the positive charge of the nucleus do in relation to the electrons?
it attracts them and keeps them in place
what is group 1 of the periodic table called?
alkali metals
as you go down group 1, the metals become more…/why
reactive/because the outer electron is more easily lost
as you go down group 1, what happens to the boiling and melting points?
they get lower
do alkali metals have low or high density?
low
how many electrons do the alkali metals have in their outer shells?
1
what happens when the alkali metals react with non metals?
they form ionic compounds (as they lose their outer electron)
what happens when the alkali metals react with water?
they react vigorously and produce hydrogen
how can you test for hydrogen?
holding a flame above the area in question. if a squeaky pop is heard, hydrogen is present
what are the elements in group 7 of the periodic table called?
the halogens
