chapter 2
hydrogen lecture 1
1766 henry cavendish was the first to
recognize hydrogen gas is discrete
substance by identifying the gas from a
metal acid reaction is flammable air
in 1781 he was the first person to find
that the gas produced water it when
burned this was key experiment in
disproving your aristotelian theory of
the four elements
position of hydrogen in the periodic
table position of an element in periodic
table depends upon its electronic
configuration and properties hydrogen
resembles with the elements of Group
wanna four on seven and some respects
properties of hydrogen do not completely
match with any one of the
above-mentioned groups that are Group
one in group for a group seven day
compared with Group one a number one
resemblance like alkali metals hydrogen
has one electron in its valence shell
number two valence shell electronic
configuration of hydrogen and alkali
metal is seen
number three both hydrogen and alkali
metals are good reducing agents
number four light alkaline metals
hydrogen can also form halides
five halides of alkali metals and
hydrogen ionized in similar weight in
aqueous solution
number six light alkali metals hydrogen
can also form compounds with nonmetals
difference with Group one
hydrogen is a non-metal where is
elements of one you'll our metals
number two hi
form both covalent and ionic compounds
but alkali metals only form ionic
compounds
number three hi
cannot lose its valence electron
four hydrogen is a gas at room
temperature but alkali metals are solids
number five unlike sodium ion or
potassium ion hydrogen ion is unstable
in water
number six ionization potential value of
hydrogen is very high compared to alkali
metals
resembles with group 4
number one valence shell of hydrogen is
half filled like the elements of group
4a
number two ionization potential and the
electron affinity of hydrogen and carbon
are comparable
number three electronegativity of
hydrogen atom and carbon family are
almost similar electronegativity of
hydrogen is two point one carbon have
two point five and silicon atom have two
point four
difference with group 4a
number one
tetravalent but hydrogen is monovalent
as carbon family members have four
electrons in their last shell so they
are tetravalent while hydrogen atom had
only one letter n' in their valence
shell so I it is mono valent
number two hydrogen is a gas at room
temperature but elements of group 4 are
solids
number three boiling and melting point
of hydrogen is very less than that of
the elements of group 4a
resemblance with group 7o
number one ball
giman halogens require one electron to
complete their valence shell
number two bow
hydrogen and halogens are nonmetals
except iodine which has partial metallic
character
number three both hydrogen and halogens
X as negative ions when combined with
metals
with group seven Oh
number one hi
has one electron in valence shell wild
halogens has seven electrons
number two unlike halide ions hydride
ion is unstable in water
in the light of above facts hydrogen
does not completely resemble with member
of any one of you have mentioned groups
that is why position of hydrogen is
still undecided the difference behavior
of hydrogen is because of the simplest
atom which possess a singly positive
charged nucleus and one electron moving
around a nucleus
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