I- Periodic Classification Flashcards
(30 cards)
General Knowledge
- No.of Periods
- No. of groups
- No. of blocks
- 7 periods
- 18 groups (1 to 18 grps)
- 4 blocks (s,p,d,f)
General Knowledge
What are representative elements?
All a. s-block
b. p-block
c. including noble gases
because they represent general properties of their groups (not asked)
General Knowledge
What are transition elements?
D block elements EXCEPT GRP 12
(n-1)d subshell incomplete either in ground or stable oxidation state.
36 transition elements in periodic table.
General Knowledge
What are inner transition elements?
All F-block elements
Electronic Configuration
GEN EC of period?
ns (n-2)f (n-1)d np
1= s 2= s,p 3=s,p,d 4=s,p,d…..
Electronic Configuration
EC of Noble Gases
He- 2
Ne- 10 (2 + 8)
Ar- 18 (2+8+8)
Kr- 36 (2+8+8+18)
Xe- 54 (2+8+8+18+18)
Rn- 86 (2+8+8+18+18+32)
Electronic Configuration
No. of electrons in each subshell
- s= 2
- p= 6
- d= 10
- f= 14
equates to no. of elements in each period(check n)
IUPAC
0-9 of IUPAC
- 0= nil
- 1= un
- 2= bi
- 3= tri
- 4= quad
- 5= pent
- 6= hex
- 7= sept
- 8= oct
- 9= enn
add ‘ium’ to end of element
Identification
- When Z is given, how to identify group and periods?
- Group no: 18+ Z- (Atm. no. of next noble gas)
Eg:- Zn=34 Group= 18 + 34 - (36) - Period no: Period of next noble gas
He-1
Ne-2
Ar-3
Kr-4
Xe-5
Rn-6
Og-7
Identification
For elements between >= 104, Group and Period is?
Period= 7
Group = Last two digits of Z. (104- Grp 4)
Identification
If EC of an element is given, group and period is?
period= value of n(highest)
Group= count no. of electrons, find Z.
Zeff
What is Zeff?
A- Actual
A- Attractive
P- Power
O- Of
N- Nucleus
Zeff
Equation of Zeff
Actual attraction= attraction - repulsion
Zeff= Z- σ
Z= nuclear charge/ no. of p+ σ=screening or shielding constant
Zeff
Order of σ
s > p> d> f
highest screening/shielding=s [sizes inc. less Zeff]
Zeff
Period Order of Zeff
- In a period, Zeff inc [charge inc, more attraction/binding]
- In isoelectronic species,
-ve charge↑ Zeff↑ +ve charge↑ Zeff ↓
[↑ electrons, ↑ AAPON, size decrease] Zeff∝ -ve Zeff∝ 1/-ve
Zeff
In which elements can screening effect be NOT seen?
Hydrogen and single e- species
Atomic Radius
What is atomic radius? What difficulties are there in measuring it?
-distance between nucleus and outermost electron in an isolated gaseous atom
-has 3 difficulties
1. size of atom is very small
2. boundary of atom is NOT well defined
3. Isolation of a single atom is very difficult.
Atomic Radius
What is Covalent Radius?
-used in covalently bonded elements
-half of internuclear distance in uniformly (Cl-Cl, C-C) covalently bonded molecules.
- r= Inter nuclear distance/2
Atomic Radius
What is Metallic Radius/ Crystal Radius?
-used in metals
-in metals atoms exist as kernels i.e positively charged ions (nucleus+ other electrons) and a sea of outermost electrons.
- r= D/2 [D= metallic bond length]
- r ∝ 1/metallic bond strength
- EXCEPTION:- r[Cr] < r[Mn] [As Mn has weak metallic bonds]
Kernels are held together by metallic bonds and there exists electrostatic force of attraction between kernels and electrons
Atomic Radius
What is van-der-waals radius?
-used mainly for noble gases as they are inert
- two noble gase atoms are brought as much closer as possible and distance between their nucleus is measured.
- r = van-der-waals-diameter/2
Vander waal’s forces are weak electrostatic forces that attract neutral moleculues to one another.
Atomic radius
Relation between r꜀, rₘ, rᵥ
r꜀ < rₘ < rᵥ
Atomic radius
What is ionic radius?
-The distance from the nucleus of an ion to its outermost electron.
i.r ∝ -ve charge
i.r ∝ 1/ +ve charge
- Na+ < Na < Na-
Size
Variation
- Periods: Zeff ↑ size ↓
- Groups: no. of shells↑ size↑
IE
What is ionization energy?
- the amount of energy required to remove an electron from an isolated gaseous atom.
- always** +ve**
