C2 - The Periodic Table - C2.1, C2.2, C2.6 Done Flashcards
Why was it so hard for scientists in the 1800s to categorise elements?
As they were finding new ones every year, and they did not know much about the ideas of atoms and the difference between chemical compounds and elements
How did John Dalton categorise the elements?
He arranged them by their atomic weights, which had been found out through multiple chemical reactions of them with each other
How did Newlands build on the ideas of Dalton?
He categorised them by their masses, and realised that every 8th element was similar. This lead to him categorising them in 8s, but he assumed all the elements had been found, and so some were forced into places where they did not necessarily fit
How did Mendeleev arrange the elements in his breakthrough?
He categorised them so that there were regular intervals in the properties of the elements, and were arranged in order of their mass. He left gaps where there were missing elements which were later filled in when they were discovered
What problem did Mendeleev’s model face?
Not all elements fit with his pattern - some had oddly heavy weights but not a reactivity that fit with them. He grouped these by ignoring the mass problem and keeping the reactivity similar. Isotopes accounted for many of these problematic elements
What is a group in the periodic table?
A group is a vertical line of elements
What is a period in the periodic table?
A period is a horizontal line of elements
What does the group number tell you about the elements in that group?
How many electrons those elements have in their outer shells
Give 2 main differences between metals and non-metals?
Metals conduct electricity whilst non-metals are often electrical insulators, metals often have higher melting and boiling points, and they are ductile whilst non-metals are often brittle
Are the noble gases diatomic, triatomic, or monatomic?
Monatomic, as they have full outer shells and so have no need to bond to another atom to gain a full structure
What are the qualities of the noble gases and why are they as such?
They have very low melting and boiling points, and are very unreactive. This is because they have full outer shells, and so are stable and do not gain or lose electrons easily
Do metals tend to gain or lose electrons, and what about non-metals?
Metals lose, non-metals gain (often)
What are 2 physical qualities of the transition elements?
They are good conductors of electric and thermal energy / they are hard and strong / they have high densities / they have high melting points, except mercury which is liquid at room temperature
How reactive are the transition elements?
The transition elements are not the most reactive - in water and oxygen they barely react on comparison to the alkali metals
Why are there often roman numerals next to the ions of transition element compounds?
This is as they can form more than one ion and so the numeral tells you which one it is
