The ionisation energy is the energy required to remove electrons from the outer most shells of the electron is called ionisation energy.
It decreases down the group because -
-As we move down the group the size of the elements increases
-The distance between the nucleus and the outer most electron also increases.
-This leads to a decreased force of attraction between the nucleus and it becomes easier to remove them.
Similarly when we move across the period the number of electrons in the same shell increases which leads to strong forces of attraction and the ionisation energy increases.
As a result, it is easier for valence shell electrons to ionize, and thus the ionization energy decreases down a group. ... This is due to valence shell stability. The ionization energy of the elements within a group generally decreases from top to bottom. This is due to electron shielding.
hope it helps..!!
Ionization energy is the amount of energy required to remove an electron from outer most valance shell of a gaseous atom.
GROUP: It decreases in group due to increase in the size of an atom, shielding effect and decrease in the nucleus charge showing that the hold of nucleus on the outer most shell becomes less and it becomes easy to remove electrons from the outer most shell. :))
suppose the edge length of the unit cell = a
radius of the sphere = r
then,since the sphere are each other along the edge,therefore a = 2r
now there are 8 spheres at the corners of the cube & each sphere at the corner is shared by 8 unit cells & the contribution per unit cell is 1/8 so that
number of spheres per unit cell is 8 x 1/8 = 1
volume of sphere =4/3πr3 & volume of cube = a3 = (2r)3 = 8r3
now packing efficiency = (volume of one sphere / total volume of cubic unit cell) x 100
(4/3 πr3 / 8r3) x 100 = 52.4%
therefore the volume occupied in simple cubic arrangement = 52.4%
(ii) body centered cubic:
let us suppose the edge leght = a & radius of each sphere = r then there are 8 spheres at the corners & 1 in the body of unit cell
therefore number of spheres per unit cell = (8 x1/8) + 1 = 2
now volume of unit cell = a3 = (4r / √3)3
and volume of a sphere = 4 / 3πr3
total volume of two spheres = 2 x 4/3πr3
packing efficiency = (volume of two spheres in unit cell/total volume of unit cell ) x 100
= (2 x 4/3πr3 / (4r/√3)3 ) x 100 = 68%
law of conservation of mass states that mass is an isolated system and is neither created nor destroyed by chemical reactions or physical transformations. according to , mass of the products in a chemical reaction must equal to the mass of the reactants.
hope it dear