Fill in the blanks:
(i) Nuclear fusion is possible only at an extremely high temperature of the order of ____K.
(ii) The phenomenon of radioactivity is exhibited by elements having atomic number_____.

Fill in the blanks: (i) The third period contains____elements. (ii) _____ is defined as half the distance between the nuclei of adjacent metal atoms.

Classify the following statements into true or false. i. Radioactivity is unaffected by pressure and temperature. ii. Radioactivity is affected by large electric and magnetic fields. iii. The rate of disintegration of a radioactive substance at a particular time is directly proportional to the number of atoms present initially. iv. Nuclear force is charge independent but it depends on the relative orientation of the spins.

Fill in the blanks (i) A tangent to a circle touches it in …... Point (s). (ii) A line intersecting a circle in two points is called a ….. (iii) Number of tangents can be drawn to a circle parallel to the given tangent is …. (iv) The common point of a Tangent to a circle and the circle is called ..... (v) We can draw ..... tangents to a given circle. (vi) A circle can have ..... parallel tangents at the most.

Which of the following is/are correct ? (I) Density of all the nuclei is same. (II) Heavy elements exhibit radioactivity. (III) Amongst alpha, beta and gamma rays, alpha -particle has minimum penetrating power. (IV) Isobars are the atoms of same elements having the different mass number.