What is periodicity? What are periodic properties?

SHORT ANSWER: Periodicity means, something repeats after fixed interval. Periodic properties in chemistry means that if elements are arranged in an order, the properties of elements would repeat after some period. COMPLETE ANSWER: Period: Time interval Peridiocity: Thing repeats after this time interval. Example: See the following pattern- a, b, c, a, b, c, a, b, c, ... So the pattern a, b, c repeats after interval of 3: a,b,c then a,b,c then a,b,c ... Properties: How things behave. Example: Property of sugar: Sweet Property of chilly: Its spicy. Periodic Properties: Properties repeat after an interval. In Chemistry, when elements are arranged in order of increasing atomic number, the properties repeat. Example- Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar Properties of Li are like Na, Be like Mg, C like Al, N like P, etc... read less

Anything which repeats itself after a certain(regular 0 interval is called periodic and this behaviour is termed as periodicity. It is the similarity in the outer electronic configuration which gives rise to the periodicity in the properties of the elements. For example all alkalies metals have the outer electronic configuration of the type ns1 Periodic properties are atomic radius: many physical and chemical properties of an element depend upon the size of atom.the distance from the centre of the nucleus to the outermost shell of electrons in the storm of any element is called its atomic radius.because of the many reason s the estimated atomic radii are called effective atomic radii. the atomic sizes are generally expressed in terms of the following radii:- (i) covalent radius; it is defined as half the distance between the nuclei of the two similar atoms covalently bonded to each by a single (ii)metallic radius; it is defined as the half the distance between the nuclei of the two adjacent metal atoms in a closed packed lattice of the metal. (iii) vander waals radius: it is defined as the half the inter nucleur distance between similar adjacent atoms belonging to the two neighbouring molecules of the same substance in the solid state. the atomic radius decreases while going from left to right in a period. the atomic radius increases in moving from top to the bottom in a group the atomic radii of the ions belonging to the same group of elements and having identical charges increase in going from top to the bottom in GROUP. Ionisation enthalpy: the amount of energy required to remove the most loosely held electron from an isolated gaseous atom in its ground state is called ionisation enthalpy. the ionisation enthalpy decreases in going from top to the bottom in a group. the ionisation enthalpy increases as we go from left to right in a period. Electron gain enthalpy: it is the molar enthalpy change when an isolated gaseous atom or anion in it ground state adds an electron to form the corresponding anion.it is decreases in going from top to bottoming a group. it is increases across a period in going from left to right. Electronegativity: the relative tendency of an atom in a molecule to attract a shared pair of electrons towards itself is called electronegativity. It decreases down the group. It increases from left to right in a period. Valence: the chemical behaviour of an element depends upon the number of electrons in the outermost shell of its atom. All elements in a group show the same valency. The valence electrons increases in going from left to right in a period. Hence valency of elements in a period first increases and then decreases. Melting and boiling point:the melting and boiling point s of alkali metals decrease down the group. Melting and boiling points of alkaline earth metals decreases down the group. Melting and boiling point of alkaline earth metals are higher than their of alkali metals. The melting and boiling points of halogens increase down the group Metallic character: in a periodis decreases from left to right. It increases down the group. Non metallic character: it decreases as we go down in a group. It increases in going from left to right across a period. Chemical reactivity of metals: it decreases in a period from left to right. It increases down the group. Chemical reactivity of non metals: it increases from left to right in a period. in a group decreases as we go down the group. read less

Certain basic Properties (Atomic Size, Shielding Effective, Effective Nuclear Charge and Electronic Configuration) of different elements tend to influence some measurable properties of those elements in such a manner that they show regular trends in those properties along a period or a group of the periodic table. This trend in properties is called as periodicity. read less

Periodicity refers to a property possessed by the elements of the Periodic property wherein after a particular interval the properties of elements repeat themselves. eg: lets take an example of sodium(Na). it is a highly electropositive element. Similarly potassium(K), has high electro-positivity. based on periodicity, the elements are grouped in to groups.. i.e. elements in group 1 have similar properties. read less