Question

Identify the group with atomic number equal to 19.
A.Halogen
B.Chalcogen
C.Noble gas
D.Alkali metal

Answer 1

The atomic number, also known as the proton number of an element represents the number of atoms which are present in the nucleus of every atom of that element. It is designated by the symbol Z. The atomic number 19 belongs to the element potassium.

Complete step by step answer:
Let us check the given four options one by one.
Halogen: The group 17 of the periodic table consists of five elements. These are fluorine, chlorine, bromine, iodine and astatine. These five elements are all non-metallic elements and they are collectively called halogens. Halogen means sea salt formers as the salts of the first three elements occur in sea water. The atomic numbers of fluorine, chlorine, bromine, iodine and astatine are respectively 9, 17, 35, 53 and 85. So, option A is not correct.
Chalcogen: The group 16 of the periodic table consists of five elements. These five elements are oxygen, sulphur, selenium, tellurium and polonium. The elements of this group show a gradual increase in metallic character on moving down the group and they are collectively called as chalcogens. Chalcogens mean ore forming elements because many metal oxides appear as oxides and sulphides. The atomic numbers of oxygen, sulphur, selenium, tellurium and polonium are respectively 8, 16, 34, 52 and 84. So, option B is not correct.
Noble gas: The group 18 of the periodic table consists of six monatomic gases which are helium, neon, argon, krypton and xenon. These elements are also known as noble gases because of their similarity with noble metals like gold and platinum which show reluctance to react rather than complete inertness. The atomic numbers of helium, neon, argon, krypton and xenon are respectively 2, 10, 18, 36, 54 and 86. So, option C is not correct.
Alkali metal: The first group of the periodic table consists of six elements which are lithium, sodium, potassium, rubidium, cesium and francium. These elements are also called alkali metals as their hydroxides are very strong alkalies. The atomic numbers of lithium, sodium, potassium, rubidium, cesium and francium are respectively 3, 11, 19, 37, 55 and 87. Thus, the atomic number 19 belongs to potassium which is an alkali metal.

So, option D is correct.

Note:
Oxygen of the chalcogen family is the most abundant of all elements. It occurs in the free state as dioxygen and occupies about 23 percent by mass of the atmosphere. Most of the oxygen which is present in the atmosphere is produced by the process of photosynthesis.
Of all the halogens, fluorine is the most reactive and hence it is also called as super halogen. Astatine is radioactive , so occurs in nature only in traces.
All other noble gas except radon are present in very small amounts in the atmosphere and so, they are also known as rare gases. They are also referred to as aerogenes.