Deck 1 Flashcards
whats the most abundant element in the universe
hydrogen
comment on melting and boiling points of hydrogen
very low melting and boiling points due to weak molecular forces
where does hydrogen comes from
in the lab - reaction of acid with electropositive metals
electrolysis - passing electricity through water
ionic hydrides
form with reactive metals where H has a -1 oxidation state
covalent hydrides
form with nonmetals (H has a +1 oxidation state)
what are the group 1 elements also known as
alkali metals
why are the group 1 elements called this
they react with water to form alkaline solution
why are they normally stored under oil
because they are so reactive.
only has one electron in their outer shell and easily lose their single valence electron (easily oxidized)
what happens when alkali metals react with water
react violently with water to form MOH and release hydrogen gas
what happens when group 1, Alkali Metals react with halogens
for salts of the form MX
eg. 2Na + Cl2 -> 2NaCl
what happens when Alkali Metals react with Oxygen in the air
create oxide coating/tarnish
Li2CO3
lithium carbonate
- drug for bipolar disorder
- used in manufacture of ceramics and toughened glass
KNO3
potassium nitrate
- gunpowder and fireworks
NaOH
sodium hydroxide
- used to make bleach
- important industrial base
what are the group 2 elements also known as
alkaline earth metals
compare group 1 and group 2
group 2 metals are harder and denser than group 1 metals
group 2 melting points are similar to group 1 boiling points
what happens when group 2 elements react with oxygen
group 2 metals reduce oxygen to form oxides
beryllium anomalous behaviour
- high charge density, Be polarizes nearby electron clouds
- can form bonds that are more covalent in character
- Be is electron deficient in linear structure (it doesnt fill its octect)
why do the first members of each non metal group act different from the other group members
- smaller size
- greater ionization energy
- only have four valence orbitals
what is the other name for group 13
Boron family
whats different about Boron compared to the rest of group 13
boron is a semimetal
- black
- hard
- high melting point
- semiconductor - tends to form covalent bonds
properties of the other group 13 elements
shiny
relatively soft
malleable
low melting
inert pair effect
just losing 1 p electron can allow ……
what is borohydride anion (BH4-) formed from
borane (BH3) with hydride (H-)
amphoteric
can react with acid or base
what are the group 14 elements also known as
carbon group
talk about the variety of chemistry in the carbon group
non metals (carbon): solid covalent bonds, very high melting points
semimetals (silicon, germanium): weaker covalent bonds, high m.p
metals (tin and lead): metallic bonding, lower m.p
carbon monoxide (CO)
produced in inefficient combustion
it is poisonous
binding to iron in hemoglobin
carbonic anhydrase
catalysis the formation of carbonic acid in blood
allotropes
different forms of elemental carbon
why does graphite conduct electricity
there is delocalization of electrons in p orbital
buckminsterfullerene
discrete C60 molecular units
why do Si=Si bonds not usually occur
Si is larger than C and forms longer bonds
key difference between C and Si
C forms unsaturated bond to give molecular gas and oxygen
Si forms tetrahedral networks
what is the vital ingredient in semiconductors
silicon
how can pure silicon be isolated
high temperature
P-type doping
introducing a hole
replacing the Si with B, Al, Ga or In (they have less electrons)
N type doping
adding group 15 donors (P, As, Sb and Bi)
resulting in an extra valence electron
phosphorus allotropes
elemental phosphorus - extremely flammable
white phosphorus - P4 tetrahedra
if you heat it in 300 degrees Celsius with no air you get
red phosphorus
phosphorus oxides
combustion of P4 gives phosphorus (III) oxide or phosphorus (V) oxide depending on whether there is excess oxygen
how many valence electrons does group 16 (oxygen family) have
six valence electrons
what are the group 18 elements also known as
noble gases
talk about the boiling and melting points of group 18 elements
extremely low boiling and melting points, very limited intermolecular interactions holding them together
applications of noble gases
helium: used to fill balloons and lighter then air craft
liquid helium: important coolant for superconductors and powerful magnets
neon: lights and signs
reactivity of group 18
very limited due to full valence shells
exception: xenon gas has been shown to react upon heating with flourine gas.
characteristics of molecular hydrogen (H2)
colourless and odourless gas
Which main group element has a common molecular allotrope made of four atoms arranged at the corners of a tetrahedron
phosphorus
what is the only halogen that is a liquid at room temperature
bromine
