Alkaline earth metal are the elements present in II group in the periodic table and are known as 'Metals' and have a charge of +2.
Alkaline earth metals - Be , Mg Ca, Sr , Ba, Ra
Halogens are present in VII A group in the periodic table and are 'Non-metals' and have a charge of -1.
Halogens - F, Cl, Br, I, At
When Alkaline earth metal (metals) combine with Halogens (non-metals) the compound formed will be ionic compound and the formula of the compound will be based on the charges of the element.
When we write the formula of the ionic compound the charges of the elements get criss crossed.
For example - Mg (Alkaline earth metal) have a charge of +2 and Cl (Halogen) have a charge of -1 and when they combine to form the formula their charges get criss crossed and we will get 
or 
When an alkaline earth metal, A, reacts with a halogen, X, the formula of the Ionic compound formed should be 
Answer:
Mole fraction is 0.2
Explanation:
You have to apply the colligative property about vapour pressure which formula is:
ΔP = P° .Xm
Where ΔP = P° - P
Pressure of vapour from pure solvent (P°) - Pressure of vapour from solution
40 Torr - 32 Torr = 40 Torr . Xm
8 Torr / 40 Torr= 0.2. > Xm
Isotopes of an element will contain the same number of protons and electrons but will differ in the number of neutrons they contain. In other words, isotopes have the same atomic number because they are the same element but have a different atomic mass because they contain a different number of neutrons.
Answer:
Explanation:
From the 1 g sample you have:
0.546 grams of cobalt chloride
1-0.546=0.454 grams of water
Now:
1) The salt
Of the 0.546 g, 0.248 g are cobalt (Mr=58.9) and the rest id Cl (Mr=35.45):
Dividing:
So the molecular formula will be:
2) The water
The water's molecular weight is M=18 :
Bonding with the Co:
The complete formula of the hydrate:
