VALENCY

VALENCY

The combining capacity of an atom is called as VALENCY of it.

It is a number(without positive or negative signs)

It is not a constant value.

To determine valency we use below: 

The number of Hydrogen atoms attached to an atom is the VALENCY of it.

examples:

1)Water (H₂O)=O valency is 2

2)Ammonia (NH₃)=N Valency is 3

3)methane (CH₄)=C Valency is 4 etc.

The number of chlorine atoms attached to an atom is the VALENCY of it.

Examples:

1)HCl=H valency is 1

2)CaCl₂= Ca valency is 2

3)PCl₃=P valency is 3

4)CCl₄=C Valency is 4 etc.

Double the number of Oxygen atoms which are attached to an atom is the VALENCY of it.

1)CaO=Ca valency is 2

2)CO=C Valency is 2

3)CO₂=C Valency is 4

4)P₂O₃=P valency is 3

5)As₂O₅=As valency is 5 etc.

The number of electrons lost by an atom to form cation is the VALENCY of it.

examples:

Hydrogen ion - H⁺ =valency is 1

Lithium ion - Li⁺=valency is 1

Sodium cation - Na⁺ =valency is 1

Magnesium ion - Mg²⁺=valency is 2

Calcium ion - Ca²⁺=valency is 2

Zinc ion - Zn²⁺=valency is 2

Aluminium ion-. Al⁺³=valency is 3

Ferric ion - Fe³⁺=valency is 3 etc.

The number of electrons gain from an atom to form Anion is the VALENCY of it.

Examples:

Hydride ion - H⁻=valency is 1

Fluoride ion - F⁻=valency is 1

Cloride ion - Cl⁻=valency is 1

Sulfide ion - S²⁻=valency is 2

Oxide ion- O²⁻=valency is 2

Nitride ion- N³⁻=valency is 3

Carbide ion-C⁴⁻=valency is 4 etc.

The number of electrons(unpaired electrons in last shell)shared by an atom to form chemical bonds.(The number of bonds around an atom)

The number of electrons present in last shell of an atom is it's valency.

For IA group to IVA group elements

VALENCY=ITS GROUP NUMBER 

IA=1

lithium (Li), 

sodium (Na),

potassium (K),

 rubidium (Rb),

cesium (Cs),

 francium (Fr).

IIA=2

Beryllium (Be)

Magnesium (Mg)

Calcium (Ca)

Strontium (Sr)

Barium (Ba)

Radium (Ra)

IIIA=3

Boron (B)

Aluminum (Al)

Gallium (Ga)

Indium (In)

Thallium (Tl)

IVA=4

Carbon (C)

Silicon (Si)

Germanium (Ge)

Tin (Sn)

Lead (Pb)

For VA group to VIA group elements

VALENCY=8 - GROUP NUMBER 

VA=8-5=3

Nitrogen (N)

Phosphorus (P)

Arsenic (As)

Antimony (Sb)

Bismuth (Bi)

VIA=8-6=2

Oxygen (O)

Sulfur (S)

Selenium (Se)

Tellurium (Te)

Polonium (Po)

VIIA=8-7=1

Fluorine (F)

Chlorine (Cl)

Bromine (Br)

Iodine (I)

Astatine (At)

VIIIA=8-8=0

Helium (He)

Neon (Ne)

Argon (Ar)

Krypton (Kr)

Xenon (Xe)

Radon (Rn)

In ions, the number after removing of positive and negative signs is indicating it's valency.

VARIABLE VALENCY:

A Single element which exhibits different valencies.

Elements that exhibit variable valency most commonly are transition metals(d-block elements). These elements have partially filled d-orbitals in their electron configuration, allowing them to lose or share electrons in various combinations.

Examples: 

Ferrous- Fe(ll)

Ferric -Fe(lll)

Cuprous - Cu(l)

Cupric - Cu(ll)

(Silver)Argentous-Ag(l)

Argentic -Ag(ll)

Stannous -Sn(ll)

Stannic -Sn(lV)

(Gold)Aurous -Au(l)

Auric -Au(lll)