Chemistry- the periodic table Flashcards
What did Mendeleev do differently to Newland?
He left gaps for undiscovered elements and moved some elements around
How did Mendeleev justify changing some element’s positions?
He said previously the data was badly measured!
Why did scientists dislike Newland’s theory of “the law of octaves?”
-why do it according to a piano of all things?
-two elements in some boxes
-he didn’t explain it
what are the modern versions of eka-silicon and eka-aluminium? (respectively)
germanium and gallium
Give two important differences between Mendeleev’s and the modern periodic table
-Elements are ordered due to atomic number, not mass
-no noble gases
-there are more groups- transition metals- ih the modern table
What is the definition of atomic mass?
The relative weight of each element, compared to carbon
What is the trend with softness in g1 metals?
they get softer to cut further down the group- and they’re quite easy to cut in the first place
What is the trend in density in g1 metals?
all are not very dense- top three can float on water, and density generally increases down the group
What is the trend in melting point in g1 metals?
low- Li (181) -> Cs (28)
They get lower because the ions get weaker, and the free electrons are further away from the positive nuclei
What five things would you see when you put a g1 metal in water?
-fizzing
-spits, flares or flame
-sodium + potassium melt
-float
-move around surface
What is the trend in reaction in g1 metals? (and why?)
more reactive down the group. As the atoms get larger the outer shell electron gets further away from the positive protons in the nucleus, meaning there are weaker forces between them and the electron is easier to lose
give four common features of g1 compounds
ALL ARE:
white (solids), soluble, ionic, colourless (solutions)
REMEMBER: all halogens are…
diatomic
What is the colour and state of fluorine at room temperature?
pale green gas
What is the colour and state of chlorine at room temperature?
pale yellow gas
What is the colour and state of bromine at room temperature?
red/brown liquid
What is the colour and state of iodine at room temperature?
grey solid
What is the colour and state of astatine at room temperature?
black solid
What is the colour of fluorine solution?
colourless
What is the colour of chlorine solution?
v.pale green
What is the colour of bromine solution?
orange
What is the colour of iodine solution?
brown
What is the colour of iodine gas?
purple
What is the trend of reactivity in halogens and why?
less reactive down the group- it is harder for the halogens to gain an electron as there is a larger distance between the +ve nucleus and -ve electron being gained
What is the trend of melting points in halogens and why?
higher down the group-
larger atoms, stronger IMF, harder to break
no bonds are broken.
what does OIL RIG stand for?
Oxidation
Is
Loss (of electrons)
Reduction
Is
Gain (of electrons)
does the O in Oil Rig have anything to do with the element oxygen?
No
In the equation 2Al + Cl2 -> 2AlCl3, which element has oxidised and which has reduced?
Al- oxidised (has lost electons, as it is a metal)
Cl- reduced (has gained electons, as it is a non-metal)
what do half-equations have that normal equations don’t?
electrons
do covalent/ionic molecules split up when they dissolve?
covalent: no
ionic: yes
What is the trend for boiling point and density in noble gases?
increase down the group
Why do the boiling points of noble gases increase (in whichever direction?)
as the atoms get larger, imf increase
why does helium not react?
There are no gaps in the outer shell, so it is stable and does not need to gain/lose/share electrons
why were noble gases undiscovered for much of history?
low abundance, little reactions, colourless gases
List some uses (and reasons) for uses of Helium
airships, balloons- low density
diving- does not dissolve in blood
List some uses (and reasons) for uses of Neon
lights- glows when a current is charged through
List some uses (and reasons) for uses of argon
filament light bulbs- protects wire from reacting w/ O2 or N2
List some uses for uses for krypton and xenon
lasers
List some reasons why we don’t use radon
radioactive- causes cancers and other health problems
Why do elements in the same group undergo similar reactions? **
-chemical reactions depend on outer shell electrons
-elements in the same group have the same number of outer shell electrons
What should you remember when doing “Which element is in Group X and Period Y” questions? **
Don’t count transition metals!
What should you remember when doing reaction questions? **
diatomic gases
You are given KCL, CL2, KBr, Br2, KI, I2. Prove that iodine is less reactive than bromine using the word “oxidise” **
-Add Br2 to KI
-colour change: orange-> brown
-iodine was oxidised by bromine
-iodine must be less reactive than bromine
