A neutral atom in the ground state has four electrons in its fifth and outermost principal energy level. What element is it?

Tin

Explanation:

Tin is an element which belongs to the carbon family in the periodic table. It lies in group 14 of the periodic table i.e. IV a.

The symbol of Tin is Sn. Tin has 50 electron in total. Its atomic number is 50. The 50 electrons of tin are divided in its five energy shells. The outer most or the valence shell contains 4 electrons in the ground state.

The number of electrons present per shell in tin is : 2, 8, 18, 18, 4.

The electronic configuration of tin is : [Kr] 4d¹⁰5s²5p²

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.

b is the correct answer

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