1. why chlorine and bromine are kept in a same group of periodic table?
2.explain all the elements of a group and period have similar and different chemical properties respectively?
3.why is the atomic no. of an element more important than atomic mass to know the properties of an element?
4. Lithium, sodium, pottasium are all the metals which react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?
5.Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything do there atoms have in common?
6. Why do you think noble gas are placed in a seperate group?
7. On the basis, of electronic structure how will you select
a)first element in a period
b)terminating member in a period
c)chemicaly similar elements
8. If an element with atomic no. 'A' is an inert gas.In which group would you find an element with atomic no (A+2)?
9.What properties do all elements in the same coloumnin the periodic table as boron have in common?
10. in which of the following pairs,choose the atom having the bigger size:
(i) mg(at no. 12) or cl (at no. 17) (ii) na (at no.11) or k(at no. 19)
11. Element 'X' and 'Y' belongs to group 1 and group 17 of the periodic table respectively. What will be the nature of bond in the compound 'XY' ? Give 2 proprties of XY?
Answers
1 in a group the elements have same valance shell electronic configuration. as the electronic configuration of both the elements is same i.e. they have7 electrons in their outermost shell. therefore they are kept in the same group.
2. the chemical properties of an element are mostly defined on the basis of their valancy and no. of valance electrons. the no. of valance electrons remains same in a group . therefore they are chemically similar whereas in a period the no. of valance electrons increases and hence they do not have same chemical properties.
3. the atomic no. defines all the chemical properties of an element . for ex. the isotopes of an element do have the same chemical properties but it is not the case with the isobars . they may not have the same properties. therefore atomic no............
4. yes,(they have similar valance shell configuration and hence have similar chemical properties because of same valancy.)
5.both of these gases have completely filled outermost orbit which gives them the property of unreactivity.
6.they are placed in a different group because
1. they have completely filled outermost orbit.
2. they have different chemial properties as compared to other elements.
7.a) the element having 1valance electron would be the first in the period.
c) he elements having similar no. of valance electrons.
8.2nd group
9. same valancy and same no. of valance electrons, similar formula of oxides.
10. Magnesium (Mg) ; potassium (K)
11. ionic bond.
a)high melting point and boiling point.
b) Dissociate into ions when dissolved in water