The structure of the periodic table is based on the distribution of a- protons b- electrons in each element. the elements are arranged in horizontal a- periods b- groups vertical a- periods b- groups

B- electrons, A- periods, B- groups

The correct answer is Option A, Option A and Option B.

Explanation:

Elements in a periodic table are distributed in 7 Periods and 18 Groups.

The elements are distributed on the basis of increasing atomic numbers. Atomic number is defined as the number of protons that are present in an element.

Thus, the elements in the periodic table are distributed based on the distribution of protons.

The elements are arranged in vertical columns known as Groups and in horizontal rows known as Periods.

Hence, the correct answer is Option A, Option A and Option B.

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.