<u>Answer: </u>He sorted on the basis of average atomic weights.
<u>Explanation:</u>
Dmitri Mendeleev in 1863 arranged chemical elements in the groups according to their average atomic weights.
He said that elements which have similar chemical properties either have similar atomic weights or their atomic weights increases regularly.
Hence, he collaborated a great work in sorting the elements according to their average atomic weights.
Answer:
<em>D. One negative charge</em>
Explanation:
During the formation of a bond, if an atom gains an electron, after that it will be left with a negative charge compared to the atom before the bond is formed. This is because in these types of bonds, which are <em>ionic bonds</em>, there is a <em>transfer of electrons between atoms</em>, there will be one or more atoms that yield electrons that will be captured by another and other atoms that gain them, and the difference of charges produced by this transfer of electrons, will cause the union to occur due to the attraction between electrostatic forces.
If you have a neutral atom before joining, and it gains an electron to form a bond,<em> it will have one electron more than its initial state</em> (in the initial state, the number of protons and electrons is the same, because the atoms they are electrically neutral), so having an extra electron will make it have a negative charge, since there will be a difference between the number of protons and electrons that the atom possesses. <em>This is why the correct answer is D.
</em>
In the case of <em>response A and B</em>, <em>the atom could only remain positively charged if it loses electrons</em>, but as in this case it wins, <em>they are not correct</em>.
<em>The answer C is also not correct</em> because only one electron wins, so that it is left with two negative charges, <em>it should gain two electrons during the bond formation.</em>
<u>Answer: </u>The chemical symbol of the element is Sulfur.
<u>Explanation:</u>
The element which is present in third period of the periodic table having four 3p electrons is Sulfur. Sulfur is the 16th element of the periodic table which has 6 valance electrons.
The electronic configuration of this element is: ![[Ne]3s^23p^4](https://tex.z-dn.net/?f=%5BNe%5D3s%5E23p%5E4)
This element is considered as a non-metal because it will accept electrons in order to attain stable electronic configuration.
Hence, the chemical symbol of the element is Sulfur.
Difference between Gas and Vapour:
Gas:
A thermodynamic state in which a substance exists only in one phase i.e. Gas phase. In above given examples N₂, He and CO₂ exists as gases at room temperature. These gases cannot form a solid or liquid phase along with gas phase as these states requires very low temperatures.
Vapours:
It is a thermodyanamic state in which a substance exists in more than one phase. In given options Sulfur can exist in vapor state. This is because sulfur exists in a cyclic or chain form due to catenation (self linkage property). Therefore, a lower members of S allotrops can form a vapours.
