Partielo | classification of elements

ncert notes

Definitions

law of triads

it was stated by johann dobereiner that the average mass of the atomic weights of the 1st and the 3rd element is nearly equal to aw of the 2nd element. for eg: lithium,sodium and potassium

dobereiner table

Definitions

law of octaves

john alexander newlands arranged elements in their increasing atomic weights and notes every eighth element had properties similiar to the first element true only till calcium

mendeleevs periodic table

- physical and chemical properties are periodic function of atomic masses - he arranged then known elements in order of increasing atomic mass -acc to mendeleevs there existed 9 grps and 7 periods -he predicted gallium as eka-aluminium and germanium as eka-silicon.

lother meyers classification

the alkali metals are going to be at the crest of the curve
the alkaline earth metal they will occupy the midpoints in descending portion
transition metals are going to occupy the trough
the halogens are going to occupy the ascending portion before inert gases

atomic volume =atomic mass/density

long form of periodic table or mosleys pt

he studies the frequencies of xrays produced by bombardment of beam of electrons of the metal surface
the square root of frequency is directly proportional to the effective nuclear charge i.e. atomic number

Definitions

periodic law

- the physical and chemical prop are the periodic function of atomic number - number of periods-7 - number of grps- 18

To remember :

s block

ns(1-2)
extreme left
first grp alkali metals and second are alkali earth metal

p block

ns(2) np(1-6)
extreme right
grp 13-boron family
14-carbon family
15-nitrogen or pnicogens family
16-oygen family
17-halogens
18-inert gases

d block

ns(1-2) (n-1)d(1-10)
transition elements

at no 92 onwards all elements are knows as trauranic elements
s and p block elements are collectively called representative elements
3rd period elements are called typical elements

nomenclature of elements above 100

To remember :

prediction of period and grp and block of a specific element

period of element corresponds to principal quantum number of valence shell
block of element corresponds to the sub shell in which last electron is present.
group no
for s block(grp number = number of electrons present in valence shell)
for p block(grp no=10+number of e present in valence shell)
for d block elements (grp no= no of electron present in n-1 d subshell and no of electrons present in ns subshell)

for ex :

sulphur: atomic number = 16

electronic configuration = 1s2 2s2 2p6 3s2 3p6

period = 3

block = p

atomic number = 10+ (no of valence shell electrons)6 = 16

Definitions

effective nuclear charge(z or z*)

the net positive charge experienced by the outer electrons in polyelectronic atom is called z effective.

screening effect of sheilding effect

define : the decrease in force of attraction bw the nucleus and outer electrons by the inner electrons

zeff = z-s (where s is the screening const)

slater's rule

case 1: if electron in question resides in s or p subshell

rules for case 1

then all electrons present in shells higher than electron in question contribute zero to sigma or s.
all electrons present in same shell contribute 0.35 to sigma
all electrons present in (n-1) shell contribute 0.85 to sigma
all electrons present in deeper shells contribute 1 to sigma

Q] find the zeff of last electrons of cl

ans] - 1s2 and 2s2 are one orbital all together

the deeper or innermost orbital is (n-2) for whos electrons contribution will be multiplied to 1
rest will (n-1)electrons * 0.85 and n electrons * 0.35

find the z eff for chlorine

case 2: if electrons in question is present in d or f subshell

rules for case 2:

then all electrons present in shells higher than electron in question contribute zero to sigma or s.
all electrons present in same shell contribute 0.35 to sigma
all electrons present in (n-1) or deeper shells contribute 1 to sigma

for ex: calculate the effective nuclear charge for iron

ATOMIC RADIUS

define: it is one half of the distance bw two nuclie of like atoms bonded by single covalent bond.

used for non metals
CASE 1: for homoatomic molecule the distance bw the two nuclie divided by two
CASE 2: for heteroatomic molecules and electronegativity almost zero(sum of radium of the two atoms)
for heteroatomic molecules and the electronegativity is not zero
if the electronegativity is nearly same we use the stevenson and schoomakerformula

d_a-b= r_a + r_b - 0.09|electronegativity difference of both atoms |

if the electronegativity difference is not zero then we use the porterfeild formula

da-b = ra + rb - 0.09|electronegativity difference of both atoms |²

METALLIC RADIUS

Define: it is one half of the distance bw two nearest neighbouring atom ion metal crystal.

#used for metals

Definitions

vanderwaals radius

it is one half of the distance bw nuclie of two adjacent atoms in two nearest neighbouring molecules

To remember :

Out of all the radius that we have studied so far

Vander waal radius > metallic radius > covalent radius

Q] hardik panda went to meet his brother krunal panda who was studying sirs chemistry book where he wasn't able to find theoretical value of bond length of h-f although he knew the separate radius of h(0.38 A) and f(0.72A) and electronegativity of H and F are 4 and 2. 1 respectively. find H-F bond length acc. to stevenson and schoomaker formula?

Ans]

d A- B = ra - rb - 0.09|delta X|

Ra=0.38

Rb=0.72

Delta x= 4-2.1 = 1.9

covalent bond is 0.93 angstrom

Same way for schoomaker formula

Q] the c-c bond of single bond length is 1.54 and that of c-cl is 1.98 A. If the en is 3 and 2.5 respectively find the c-cl bond length acc to both the formulas?

Ans]

ncert notes

Definitions

law of triads

it was stated by johann dobereiner that the average mass of the atomic weights of the 1st and the 3rd element is nearly equal to aw of the 2nd element. for eg: lithium,sodium and potassium

dobereiner table

Definitions

law of octaves

john alexander newlands arranged elements in their increasing atomic weights and notes every eighth element had properties similiar to the first element true only till calcium

mendeleevs periodic table

lother meyers classification

the alkali metals are going to be at the crest of the curve
the alkaline earth metal they will occupy the midpoints in descending portion
transition metals are going to occupy the trough
the halogens are going to occupy the ascending portion before inert gases

atomic volume =atomic mass/density

long form of periodic table or mosleys pt

he studies the frequencies of xrays produced by bombardment of beam of electrons of the metal surface
the square root of frequency is directly proportional to the effective nuclear charge i.e. atomic number

Definitions

periodic law

- the physical and chemical prop are the periodic function of atomic number - number of periods-7 - number of grps- 18

To remember :

s block

ns(1-2)
extreme left
first grp alkali metals and second are alkali earth metal

p block

ns(2) np(1-6)
extreme right
grp 13-boron family
14-carbon family
15-nitrogen or pnicogens family
16-oygen family
17-halogens
18-inert gases

d block

ns(1-2) (n-1)d(1-10)
transition elements

at no 92 onwards all elements are knows as trauranic elements
s and p block elements are collectively called representative elements
3rd period elements are called typical elements

nomenclature of elements above 100

To remember :

prediction of period and grp and block of a specific element

period of element corresponds to principal quantum number of valence shell
block of element corresponds to the sub shell in which last electron is present.
group no
for s block(grp number = number of electrons present in valence shell)
for p block(grp no=10+number of e present in valence shell)
for d block elements (grp no= no of electron present in n-1 d subshell and no of electrons present in ns subshell)

for ex :

sulphur: atomic number = 16

electronic configuration = 1s2 2s2 2p6 3s2 3p6

period = 3

block = p

atomic number = 10+ (no of valence shell electrons)6 = 16

Definitions

effective nuclear charge(z or z*)

the net positive charge experienced by the outer electrons in polyelectronic atom is called z effective.

screening effect of sheilding effect

define : the decrease in force of attraction bw the nucleus and outer electrons by the inner electrons

zeff = z-s (where s is the screening const)

slater's rule

case 1: if electron in question resides in s or p subshell

rules for case 1

then all electrons present in shells higher than electron in question contribute zero to sigma or s.
all electrons present in same shell contribute 0.35 to sigma
all electrons present in (n-1) shell contribute 0.85 to sigma
all electrons present in deeper shells contribute 1 to sigma

Q] find the zeff of last electrons of cl

ans] - 1s2 and 2s2 are one orbital all together

the deeper or innermost orbital is (n-2) for whos electrons contribution will be multiplied to 1
rest will (n-1)electrons * 0.85 and n electrons * 0.35

find the z eff for chlorine

case 2: if electrons in question is present in d or f subshell

rules for case 2:

then all electrons present in shells higher than electron in question contribute zero to sigma or s.
all electrons present in same shell contribute 0.35 to sigma
all electrons present in (n-1) or deeper shells contribute 1 to sigma

for ex: calculate the effective nuclear charge for iron

ATOMIC RADIUS

define: it is one half of the distance bw two nuclie of like atoms bonded by single covalent bond.

used for non metals
CASE 1: for homoatomic molecule the distance bw the two nuclie divided by two
CASE 2: for heteroatomic molecules and electronegativity almost zero(sum of radium of the two atoms)
for heteroatomic molecules and the electronegativity is not zero
if the electronegativity is nearly same we use the stevenson and schoomakerformula

d_a-b= r_a + r_b - 0.09|electronegativity difference of both atoms |

if the electronegativity difference is not zero then we use the porterfeild formula

da-b = ra + rb - 0.09|electronegativity difference of both atoms |²

METALLIC RADIUS

Define: it is one half of the distance bw two nearest neighbouring atom ion metal crystal.

#used for metals

Definitions

vanderwaals radius

it is one half of the distance bw nuclie of two adjacent atoms in two nearest neighbouring molecules

To remember :

Out of all the radius that we have studied so far

Vander waal radius > metallic radius > covalent radius

Ans]

d A- B = ra - rb - 0.09|delta X|

Ra=0.38

Rb=0.72

Delta x= 4-2.1 = 1.9

covalent bond is 0.93 angstrom

Same way for schoomaker formula

Q] the c-c bond of single bond length is 1.54 and that of c-cl is 1.98 A. If the en is 3 and 2.5 respectively find the c-cl bond length acc to both the formulas?

Ans]