Each shell contains a fixed number of electrons. The general formula of the number of electrons can be hold in n-th shell is 2n². 5th shell can hold 2x5² = 50 number of electrons.
1st shell contains 2 X 1²= 2 number of electrons, 2nd shell contains 2 X 2²=8 number of electrons, 3rd shell contains 2 X 3²=18 number of electrons, 4th shell contains 2 X 4²=32 number of electrons, 5th shell contains 2 X 5²=50 number of electrons and so on.
Answer: (a) cesium and bromine :
(b) sulfur and barium: 
(c) calcium and fluorine :
Explanation:
For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
The nomenclature of ionic compounds is given by:
1. Positive is written first.
2. The negative ion is written next and a suffix is added at the end of the negative ion. The suffix written is '-ide'.
(a) cesium and bromine: Here cesium is having an oxidation state of +1 called as 
cation and bromine 
is an anion with oxidation state of -1. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral 
called as cesium bromide.
(b) sulfur and barium : Here barium is having an oxidation state of +2 called as 
cation and sulphur 
is an anion with oxidation state of -2. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral . called as barium sulfide.
(c) calcium and fluorine: Here calcium is having an oxidation state of +2 called as 
cation and fluorine 
is an anion with oxidation state of -1. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral . called as calcium fluoride.
The continuous movement of the bike or along those lines
1) it allows air, water and nutrients (salts) to penetrate the soil and reach the plant roots and not just stay on the surface of the soil where the plant can't absorb it.
Answer:
1. C. helium
2. D. oxygen and acetylene
3. B. deliquescence
4. C. cutting very hard surfaces
5. B. 3.5%
Explanation:
