1b:the periodic table Flashcards
how were elements classified in the early periodic table?
atomic weight
why weren’t the elements classified by atomic number in the early periodic table?
scientists didn’t know about the atomic structure of protons,neutrons and electrons
what was the downfall of ordering the periodic table by atomic weight?
some elements were placed in columns with elements with dissimilar properties and their were gaps because of undiscovered elements.
why did Mendeleev leave gaps in his periodic table?
to make sure elements with similar properties stayed in the same groups and for elements he thought hadn’t been discovered and allowed Mendeleev to predict their properties.
How was Mendeleev proven right for leaving gaps?
When These elements were found and their properties fit Mendeleev’s predictions.eg.ekasilicon(now known as germanium)
how did the discovery of isotopes confirm that Mendeleev was correct to take into account the properties of elements when ordering them?
isotopes of the same element have different masses but the same chemical properties so they occupy the same place on the periodic table
how did Mendeleev order the elements in his periodic table?
mainly in order of atomic weight but he did switch the order of some elements if it meant that elements with similar properties could be placed in the same group
what is the periodic table?
a table containing all known elements named because similar properties occur at regular intervals.
what does the number of a group tell us about the element’s electronic structure?
all elements in the same group have the same number of electrons in their outer shell and therefore,similar chemical properties.
what are metals?
elements which can form positive ions when they react
what are non-metals?
elements which don’t form positive ions when they react and instead form negative ions in ionic compounds or bond covalently with other non-metals
why do atoms react?
they generally react to form full outer shells.
how do atoms react to form full outer shells?
either losing,gaining or sharing electrons.
why do metals lose electrons to get full outer shells?
metals to the left don’t have many electrons to lose and the outer electrons of the metals towards the bottom are further away from the nucleus so weaker attraction.Overall,less energy needed to lose electrons to form positive ions w/full outer shell
why do non metals gain or share electrons to get full outer shells?
towards the right of the periodic table,they have lots of electrons to remove to get a full outer shell and towards the top,the outer electrons are close to the nucleus so they have a strong attraction to it so its easier to share or gain electrons to get a full outer shell
what properties do metals commonly have?[3]
1.strong but malleable
2.great at conducting heat and electricity
3.generally have high b.p and m.p so normally solid at room temp
what properties do non-metals generally have?[4]
1.dull looking and more brittle
2.generally lower b.p and m.p than metals so aren’t always solids
3.generally don’t conduct electricity
4.often have lower densities than metals
properties of alkali metals?[4]
1.silvery solids stored in oils because they’re very reactive and react with air
2.low density(first three less dense than water)
3.low m.p and b.p
4.soft
what is the reactivity trend down the alkali metals?
reactivity increases down the group.This is because G1 react by losing their one outer shell electron.
As you go down, the outer electron is further away from the nucleus
so less attraction between them and so the outer electron is more easily
so the atom loses an electron more easily
what is the m.p and b.p trend for alkali metals?
m.p and b.p decreases down the group
what is the density trend down alkali metals?
density increases down the group because the further down you go,the more atoms there are
what do compounds produced when alkali metals react with non-metals look like and do?
The compounds that are produced when alkali metals react with non-metals are usually white solids that dissolve to form colourless solutions in water
what is the general equation for a alkali metal and water reaction
alkali metal+water->metal hydroxide+Hydrogen
how do lithium,sodium and potassium react with water?
they float and move around ,fizz as hydrogen gas is produced and sometimes,the reaction gets hot enough to ignite the hydrogen
(Fizz,Float,Flame)