Question

first 20 elements with their valencies

Answer 1

first 20 elements with valancies

hydrogen-1-valency is 1

hellium-2-valency is o because it is noble gas the molecules are completely filled

lithium-3-valency is 1

berylium-unknown

boron-unknown

carbon-valency is 2,4

nitrogen-valency is 1,2

oxygen-valency is 1
 
fluorine-valency is 1

neon-unknown

sodium-valency is 1

magnesium-valency is 2

alluminium-valency is 3

silicon-valency is 2

phosphorous-valency is 3

sulphur-valency is 2,8

chlorine-valency is 1

argon-valency is 0 because it is noble gas the molecules are completely filled

pottasium-valency is 1

calcium-valency is 2

hence we can find valency of any element

for ex calcum

1s2 2s2 2p6 3s2 3p6 4s2

check out the last shell is valency shell

last shell is called valency shell so answer is 2 for calcium

THANK YOU

Answer 2

The first twenty elements with their valencies are;
Hydrogen =+1.
Helium =it is an inert gas.
Lithium =+1.
Berrylium =+2.
Boron =+3.
Carbon =+4.
Nitrogen =-3.
Oxygen =-2.
Fluorine =-1.
Neon =it is an inert gas.
Sodium =+1.
Magnesium =+2.
Aluminium =+3.
Silicon =+4.
Phosphorous =-3.
Sulphur =-2.
Chlorine =-1.
Argon =it is an inert gas.
Potassium =+1.
Calcium =+2.