the periodic table Flashcards
what does the group number tell you (columns)
how many electrons are on the outer shell
what does the periodic number tell you (rows)
how many shells there are in the electron configuration
how is the periodic table arranged today
in order of increasing atomic number
what does the atomic number tell you
how many protons are in the element/atom. also the amount of electrons, as their values are equal
what does the atomic mass tell you
the amount of protons and neutrons are in the element/atom
how was the periodic table arranged before mendeleev, and what were the problems
scientists attempted to classify the elements by arranging them in order of their atomic weights. this meant that some elements were placed in groups with elements which were not at all similar to them. ex: potassium and argon were next to each other, however potassium is an alkali metal whereas argon is a noble gas.
what did mendeleev do
mendeleev developed a new periodic table by leaving gaps for elements he thought has not been discovered yet. in some places, he changed the order based on atomic weights so that elements with the same properties were grouped together.
why do atoms react
all atoms want to have a full outer shell
what are the 2 liquids in the periodic table
bromine and mercury
describe the practical in which you measure the mass change during a reaction between calcium carbonate and hydrochloric acid. state the balanced symbol equation and the word equation for the reaction.
1) the conical flask and a known volume of hcl are weighed together and recorded
2) a measured mass of calcium carbonate is added to the hcl in the flask. this mass is recorded seperately.
3) the total mass of the flask, hcl, and calcium carbonate is recorded before any reaction occurs- this is the ‘starting mass’
4) the calcium carbonate reacts with the hcl, producing carbon dioxide, water, and calcium chloride. you would see effervescence due to the release of carbon dioxide into the atmosphere. this is known as the law of the conservation of mass, which states: while the overall mass seems to decrease, it’s important to remember that mass isn’t lost. it’s simply converted into gaseous carbon dioxide, which escapes. you’d also see the calcium carbonate gradually dissolve as it reacts with the hcl. sometimes, it may not fully dissolve. after the reaction, the flask and its contents are weighed again to determine the ‘final mass’
5) the difference between the starting mass and the final mass represents the mass of carbon dioxide gas released during the reaction. the change in mass would be negative, as the carbon dioxide escaped into the atmosphere.
CaCO₃(s) + 2HCl(aq) —–> CaCl2(aq) + H₂O(l) + CO₂(g)
Calcium carbonate + Hydrochloric acid —-> Calcium chloride + Water + Carbon dioxide
what does it mean if the mass increases during a chemical reaction
a gas from the atmosphere has reacted with your reactants
what does it mean if the mass decreases during a chemical reaction
one or more of the products are gases that get released into the atmosphere.
group 0 description
group 0 contains non-metal elements. the elements in group 0 are called noble gases. they are inert (very unreactive) because they already have a full outer shell and therefore don’t need to gain or lose any electrons in order to become an ion.
a chemical property is that they have full outer shells. a physical property is that as you go down the group, the boiling point increases because the atoms get larger, so they have stronger intermolecular forces.
why can the solvent not touch the spot of the mixture in chromatography
the ink would dissolve in the solvent and would not move up the paper
what is the distance travelled by the solvent in chromatography
the distance between the 2 pencil lines
what is the residue in filtration
the insoluble substance caught in the paper
