Rational Numbers (definition)

Q. The physical property of a substance can be measured without changing its chemical composition. Which of the following are physical properties?

1. Density
2. Flammability
3. Conductivity
4. Reactivity

Q.

The element with atomic number 15 belongs to _____ group of the periodic table.

Q. The position of hydrogen is not fixed in the periodic table, sometimes it is placed with alkali metals in 1st group and sometimes with halogens in the ${17}^{th}$ group as it resembles with alkali metal metals as well as with halogens.

1. True
2. False

Q.

The element with atomic number 51 belongs to the _____ period of the periodic table.

Q. The problem with elements being arranged in the increasing order of atomic masses is that the atomic mass does not increase in a regular manner in going from one element to next. So, it is not possible to predict how many elements could be discovered between the elements. This is why in the Modern Periodic Table elements are arranged according to their ___.

Q.

Generally, the valency of chlorine is _______

1. 1

2. 10

3. 5

4. 7

Q.

Elements A, B, C, D, E and F and their respective atomic numbers (within brackets) are given below:

A (3) , B (10) , C (11) , D (12) , E (14) , F (17).

Which of these is an element belonging to group 17 of the periodic table?

Q.

In the modern periodic table, the elements are arranged on the basis of their increasing:

1. Atomic mass

2. Atomic number

3. Charge on their ions

4. Mass number