{"id":1272,"date":"2020-11-30T09:00:38","date_gmt":"2020-11-30T03:30:38","guid":{"rendered":"https:\/\/www.aplustopper.com\/?p=1272"},"modified":"2020-11-30T12:13:44","modified_gmt":"2020-11-30T06:43:44","slug":"valency-and-atomic-radius","status":"publish","type":"post","link":"https:\/\/www.aplustopper.com\/valency-and-atomic-radius\/","title":{"rendered":"What is Valency and Atomic Radius"},"content":{"rendered":"

What is Valency and Atomic Radius\u00a0<\/strong><\/span><\/h2>\n

Valence:<\/span> <\/b>Valence (or) valency of an element was defined as the\u00a0combining power of an element with respect to hydrogen, oxygen or\u00a0indirectly any other element through hydrogen and oxygen.
\nValence of an element with respect to hydrogen is the number of\u00a0hydrogen atoms with which one atom of that element chemically combines.\u00a0Valence of an element with respect to oxygen is twice the number of\u00a0oxygen atoms with which one atom of that element combines.
\nFor example one atom of \u2018Na\u2019 chemically combines with one atom of\u00a0\u2018H\u2019 to give NaH. Therefore, the valence of Na is 1. One atom of \u2018Ca\u2019\u00a0combines with one atom of \u2018O\u2019 to give CaO. So the valency of Ca is 2.
\nIn general, the valence of an element with respect to hydrogen is its\u00a0traditional group number. If the element is in the group V or above, its\u00a0valence is 8\u2013 group number<\/i>. For example, chlorine valence is 8-7 = 1.
\nIn general, each period starts with valency 1 for 1 st group elements,\u00a0increases upto 4 with respect to the group number and then decreases\u00a0from 4 to 3 to 2 to 1 to zero in the following groups (this is applicable
\nonly for main group elements i.e., \u2018s\u2019 and \u2018p\u2019 block elements.
\nNow a days the valence of an elment is generally taken as the number\u00a0of valence shell (outer most shell) electrons in its atom. Oxidation number\u00a0concept almost is the latest subsititute to the valence concept in the modern\u00a0literatura.<\/p>\n

Atomic radius<\/b><\/span>
\nAtomic radius of an element may be difined as the distance from the\u00a0centre of the nucleus of the atom to its outermost shell.
\nAtomic radius of an element is not possible to measure in its isolated\u00a0<\/span>state. This is because it is not possible to determine the location of the\u00a0electron that surrounds the nucleus. However, we can measure the distance\u00a0between the nuclei of adjacent atoms in a solid. From this we can estimate\u00a0the size of the atom by assigning half of this distance to the radius of each\u00a0atom. This method is best suited to elements such as the metals that exist\u00a0in the solid state. More than 75 percent of the elements are metals and
\natomic radii of metals are called metallic radii<\/i>. Another way of estimating\u00a0the size of an atom is to measure the distance between the two atoms in\u00a0covalent molecules. The size of a chlorine atom is estimated by measuring\u00a0the length of the covalent bond between two chlorine atoms in a Cl<\/i>2<\/sub>
\nmolecule. Half of this distance is taken as atomic radius <\/i>which is called\u00a0as the covalent radius <\/i>of chlorine atom.
\nAtomic radius is measured in \u2018pm\u2019 (pico meter) units.
\n1 pm = 10-12m<\/p>\n

Variation of atomic radii in group<\/b><\/span>
\nAtomic radii increase from top to bottom in a group (column) of the\u00a0periodic table. As we go down in a group, the atomic number of the element\u00a0increases. Therefore to accommodate more number of electrons, more\u00a0shells are required. As a result the distance between the nucleus and the\u00a0outer shell of the atom increases as we go down the group in spite of\u00a0increase in nuclear change.<\/p>\n

\"What<\/p>\n

Variation of atomic radii in period<\/b><\/span>
\nAtomic radii of elements decrease across a period from left to right.\u00a0As we go to right, electrons enter into the same main shell or even inner\u00a0shell in case of \u2018d\u2019 block and \u2018f\u2019 block elements. Therefore, there should\u00a0be no change in distance between nucleus and outer shell but nuclear charge\u00a0increases because of the increase in the atomic number of elements in\u00a0period. Hence, the nuclear attraction on the outer shell electrons increases.\u00a0As a result the size of the atom decreases.<\/p>\n

\"What<\/p>\n

People also ask<\/strong><\/p>\n