12. Which of the following forms the basis of the modern periodic table?
a) Atomic mass
b) Atomic number
c) Number of nucleons
d) All of these
13. What happens to the electropositive character of elements on moving
from left to right in a periodic table?
a) Increase
b) Decreases
c) First increases than decreases
d) First decreases than increases
14. The electronic configuration of an element M is 2,8, 4. In modern
periodic table, the element M is placed in
a) 4th group
b) 2nd group c) 14th group d) 18th group
15. Which of the following is the correct order of the atomic radii of the
elements oxygen, fluorine and nitrogen?
a) O<F<N b) NFCO c) O<N<F d) F<O<N
16. What is the other name for group 18th elements?
a) Noble gases b) Alkali metals c) Alkali earth metals d) Halogens
17. Which of the following is the most reactive element of the group 17?
a) Oxygen b) Sodium c) Fluorine d) Magnesium
18. Which of the following elements has 2 shells and both are completely
filled?
a) Helium b) Neon c) Calcium d) Boron
19. Which of the following does not decrease while moving down the
group of the periodic table?
a) Atomic radius
b) Metallic character
c) Number of shells in the atom d) Valence electrons
20. An element x belongs to the 3rd period and 1st group of the periodic
table. What is the number of valence electrons in its atom?
a) 1
b) 3
c) 6
d) 8
02. Answer the following questions:-
1. What it dobernior triards
2. Write the reactions involves in black and white photography.
3. Double fertilisation
4. Ovulation and menstruation
5. What you will observe during chemical reaction?
6. What is electronegativity
7 what happen to the atoms as move along the period left to right?
8. What happen when metal reacts with base. Give example
9. Write the physical properties of metal
10. Oxidation
Answers
(12) option (b) Atomic number
(13) option (b) decreases
(14) option (a)4th group
(15) option (d) F <O< Not
(16) option (a) Noble gases
(17) option (a) helium
(18) option (b) neon
(19) option (d) valence electrons
(20) option (a) 1
Answer the following
(1)Dobernior triards are elements with similar properties which were identified by Johann Wolfgang Dobernior.
(2) The reaction which shows the white and black photography silver bromide, the reaction is :-
Ag + Br = AgBr ,
where Ag = silver, Br=bromine and the product formed is silver bromide (AgBr).
(3) Double fertilisation occurs when one male nucleus fuses with egg cell to form zygote and other male nucleus fuses with polar nuclei to cause triple fusion.
(4) ovulation:- it is the process by which ovary releases eggs or ovum .
menstruation :- when an egg is unfertilized ,the lining of the uterus sheds blood vessels along with the vaginal bleeding is called menstruation.
(5)The characteristics we observe during chemical reactions are :-
*change in state
*change in colour
*evolution of gas
*change in temperature.
(6) The tendency of an atom in a molecule to attract the shared pair of electrons towards itself is called electronegativity.
(7) On moving from left to right in a period of the periodic table, the Atomic size decreases as the Atomic number increases but the number of shells remains the same.Due to the increase in force of attraction between the nucleus and 0uter most shell of electrons increases which leads to decrease in size of the atom.
(8) when bases like alkali reacts with metal to form salt and hydrogen gas.
For example - sodium hydroxide reacts with zinc which gives hydrogen gas and sodium zincate .
2NaOH + Zn = H2 +Na2ZnO2
(9) Physical properties of metals :-
(a) Lustrous in nature
(b) They are ductile and malleable.
(c) Density and melting point is high.
(d) At room temperature metals are solid , except Mercury.
(e) metals are opaque
(f) good conductors of electricity
(g) metals are hard in nature except sodium and potassium which are cut with knives.
(10) Oxidation is the process of gaining oxygen during the reaction.