Chapter 1: Periodic Classification of Elements and Periodicity

Law of Triads

(Dobereiner)- law states that the atomic mass of the middle element is the mean of the other two.

Melting point and Boiling Point variation in periods

1. As we move from left to right in a period, the mp and bp increase up to Group IV-A 2. The mp and bp decrease frm group V-A to noble gases

Electron Affinity

A quantitative measurement of tendency of an atom of an element to accommodate the electron in its outermost orbital. If the atom has the tendency to accept the electron, then it will release energy and _ is represented by a - sign. If the energy is absorbed by the electron, then the _ is +.

Newland & Law of Octaves

An English chemist who gave this law in 1864. He classified 62 elements which were known at the time and arranged them in increasing order of atomic masses. He noticed that every eighth element had the same properties in common with the first element.

Non-metals

Are found at th top right of the periodic table.

Non Metals

Are present in the top right of the periodic table The greater the tendency to gain electrons, the greater the _ _ character Elements on the top right of the periodic table have maximum _ _ character. F,N , O are examples

Atomic radii (Variation in groups)

Atomic radii increase in a group from upper to downward direction (Reasons): I. The number of shells increase down the group ii. Sheilding effect increases down the group

Atomic radius

Average distance between the nucleus of the atom and its outermost shell provided the atom is assumed to be spherical.

II-A

Be Mg Ca Sr Ba Ra

Polymeric Hydrides

Be and Mg give intermediate types of hydrides. Their properties are in between ionic and covalent hydrides. They have polymeric structure and bonds are covalent in character.

Polymeric Hydrides

Be and Mg give these _ _

Oxides

Binary compouns of oxygen with elements of the periodic table

Electron Affinity

Can be expressed in i. kJ/mol ii. kcal/mo

Al -Razi

Classified elements on the basis of physical and chemical properties of substances

Period 6

Contains 32 elements. Cs, Ba, La, Hf, Ta, W, Re, Ox, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, At, Rn First two elements are s-block Next 14 elements are f-block. Next ten elements are d block Last six are p block. The fourteen elements which are f block are called are earths. They are after La, that is why they are called lanthanides. They range from Ce to Lu.

Period 3

Contains 8 elements. Also a short period. Na, Mg, Al, Si, P, S, Cl, Ar First two elements are s-block, next six are p block

Period 2

Contains 8 elements: called a short period. Li, Be, B, C, N, O, F, Ne First two elements are s-block, next six are p block

Period 1

Contains only hydrogen and helium

Atomic radii (Variation in periods)

Decrease in a period from left to the right of periodic table (Reasons): i. Due to increasing nuclear charge the outermost orbitals come closer to the nucleus ii. The number of shells remain the same iii.Shielding effect remains the same

Transuranic elements

Elements after Uranium. They are prepared in laboratories all over the world.They are synthetic elements.

Metals

Elements of I-A and II-A are good _.

Metals

Elements on the left hand side, in the center and at the bottom of the periodic table Elements like Na, K are true _

VII-A

F Cl Br I At

Dobereiner

German chemist who gave the law of triads in 1829.

Noble gases

Have outermost shells complete and gases at room temperature.

Chalcogens (VI-A)

Have six electrons in the outermost shell. They are electronegative elements.

The elements of group _ - _ and _ have their two outer most d subshells incomplete. These are called the transition elements. They all are metals.

I-B to VII-B, and VIII-B

Properties of Ionic Hydrides

I. they are white crystalline solids ii. They have high mp and bp iii. They conduct electricity in molten state iv. They have ionic bond present in them v. They are chemically reactive compounds vi.They react with H20 to evolve Hydrogen gas and give metal hydroxide vii. They are thermally unstable and liberate hydrogen gas on heating

Halogens

In group VII-A Have seven electrons in their outermost shells. The are electronegative elements

Reasons for Low Conductivity of Group V-A, VIA, VII-A

In these elements, the movement of valence electrons is generally restricted, as they air up to achieve a closed shell configuration. They form covalent molecules. The value of electrical conductance of these elements are low.

Oxidation State

Is the charge which it would carry in the most probable ionic formulation of ionic compound. ** the oxidation number is zero whe its present in the form of a free element.**

Ionization Energy/Ionization Potential

It is the minimum amount of energy which is required to remove the most loosely bounded electron frm outermost orbital in its isolated state. Explanation: Electrons are bounded to the nucleus in an aom. The electrons in the inner levels have greater forces of attraction than the outermost electrons. The outermost electrons are valence electrons. Less energy is required to remove such electrons as compared to their inner electrons. **When the second electron is removed from the outermost orbitals of unipositive ions, then higher energy is required. This is the second ionization potential.

rARE eARTH ELEMENTS

Lanthanides and Actinides ---they are rare in earth.

I-A

Li Na K Rb Cs Fr

Reason for electrical conductivity

Mainly due to the presence of of relatively large number of electrons in the outermost shell of the elements.

VI-A

O S Se Te Po

Mendeleev

Russian chemist who in 1871 discovered periodic law.

Metalloids

Some of he elements of the periodic table especially lower emembers of group III-A, IV-A, V-A have the properties of both metals and nonmetals.

Hydration Energy

The amount of heat absorbed or evolved when one mole of gaseous ions dissolve in water to give infinitely dilute solution.

Reasons for High Conductivity of Group IA, IIA, IIIA

The atoms of these elements have relatively free valence electrons. They can move around in a crystal structue. They cannot achieve a closed shell electronic configuration even by mutual sharing. For this reason, they have high electrical conductivities.

Halides

The binary compounds of halogens with other elements ofthe periodic table i.e NaCl, AlCl3, CCl4

Hydrides

The binary compounds of hydrogen with other elements i.e.NaH, CaH2 B2H6,

Electrical conductivity

The capability of a substance to conduct the electric current due to the free electrons without changing the composition of the substance.

Ionic radius

The distance from the center of a charged atom to the periphery of the effective sphere. When electrons are removed frm the atoms, positively charged ions are produced. The radii of positively charged ions are smaller than the neutral atoms. Reason-Due to the greater attraction of nuclear charged the remaining electrons of the ions are drawn closer to the nucleus.

Relationship of oxidation state and group number

The electronic distribution of elements in a particular group remains the same. The number of electrons in a valence shell mostly decide about the oxidation state.

Alkali Metals

The elements of the I-A group They have one electron in their outermost orbital. The have the properties to form strong alkalies with water.

Electrical conductivity of transition elements

The elements of transition metals show abrupt changes in electrical conductance. Anyhow, when we go left to right in the periodic table there is an interesting correlation. its weird, see page 22

Melting and Boiling point characteristic hydrides

The greater size of the central atom increases the mp and bp of a hydride molecule. Howevr, the first member of every group makes such hydrides which have exceptional behavior

Metalloids

The lower elements of groups III-A, IV-A V-A

Electron Affinity

The minimum amount of energy which is released or absorbed, when an electron is added to an isolated neutral gaseous atom in its lowest energy state to produce an anion.

Melting point and Boiling Point variation in groups

The mp and bp of group I-A, II-A, III-A, IV-A decrease down the group due to lesser binding energies. The atomic sizes increase down the group. The elements of group V-A, VI-A, VII-A and zero group elements show increase of mp and bp down the group

Periodic Law

The properties of elements are the periodic function of their atomic masses.

Alkaline earth metals

The they have two metals in their outermost orbital. They are present in the Earth's crust and have alkaline character.

Effect of oxidation state of the metal on the nature of oxides

There are certain metals which have variable oxidation states. So they give various oxides. Greater the oxidation number of the metal, the greater the acidic nature of the oxides.

Ionic Hydrides

These are the hydrides of alkali metals and alkalineearth metals except Be and Mg.

Period 7

This is an incomplete period. At present it consisted of 24 elements. All the elements of this period are radioactive. They are from Fr to atomic number 110.

Period 5

This period contains 18 elements. This is a long period. Rb, Sr, Y, Zr, Nb, mO, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, I, Xe First two elements are s-block Next ten elements are d -block and next six elements are p-block

Period 4

This period contains 18 elements. This is called a long period. K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Kr First two elements are s-block Next ten elements are d -block and next six elements are p-block. This is the first period which has d-block elements.

Covalent Halides

Those halides in which the bonds are produced due to the sharing o electrons between halogens and the other elements . The electronegative elements or non-metals are mostly responsible or such types of halides. Metalloids also give _ _. Elements of group IV-A, V-A, VI-A give _ _.

Polymeric Halide

Those halides which have the polymeric structure and have partially ionic bonding alog with the layer of chain lattices.Involves elements like Be, Ga, and Al

Ionic Halides

Those halides which there is ionic bond between metal and the halogen

Covalent Hydrides

Those hydrides which have covalent bonds present in them. Elements of group III-A, IV-A, V-A, VIIA- give covalent hydrides. Anyhow B and Al give complex hydrides.

Acidic Oxides

Those oxides when dissolved in H2O give the acidic solution. Oxides of carbon, nitrogen, and sulphur

Amphoteric Oxides

Those oxides which have acidic and basic character

Basic Oxides

Those oxides which yield bases in H2O, and are mostly made up of metal oxides. The elements of I-A, and II-A groups except Be and the elements of the II GROUP except Zn form...

Oxidation states of transition elements

Transition elements are shown in B subgroups of the periodic table. They also show the oxidation state according to their group number.

Variable oxidation states

Transition elements have greater number of electrons in d and f subshells. They can show variation in oxidation state. It depends on the fact that hich substance is going to react with that element

Moseley

Was a British physicist who in 1913, prepared periodic table.

pm

What atomi radii are expressed in

Second Electron Affinity

When a second electron is added to an anion, the process is endothermic due to the repulsion. Hence energy is supplied to form a dinegative ion. This energy is given positive sign and is called _. The reason is that energy is absorbed and positive sign is given to the endothermic process.

Negatively charged ion

When the electron is provided to the atom, negatively charged ion is produced, which is bigger in size than the neutral atom.

Variation of oxides in a period

When we travel from left to right in a period, the oxides become more acidic in nature.

Variation of oxides in a group

When we travel from upper to the downward direction in a group; then there happens an increase in basic character of the oxides. BeO is least basic, while Bao has maximum basic character.

I-A, II-A elements

Whenever they are dissolved in water, they give bases. With the increase metallic character of the elements down the group the oxides of the elements of the same group become more and more basic. CO2 and SiO2 are acidic oxides, GeO2 and SnO2 are amphoteric oxides, while PbO2 is basic oxide.

VIII-A (iNERT gASES/nOBLE gASES

chemically inert due to the compete outermost shells

`Variation of atomic radiii in transition elements

d-and f-block elements are transition elements. Whenever we go from left to right in transition elements, there happens to be a decrease in atomic radii for the firrst four members, but after that atomic radii show non-systematic behavior.

Factors affecting the ionization energy values

i. Atomic Size- Greater the atomic size of the atom, the smaller the ionization energy value ii. Nuclear Charge-Greater the nuclear charge, the greater the ionization energy value iii. Shielding Effect-Is a decreasing force of attraction between the nucleus and the outermost electrons due to inner electrons. The greater the shielding effect,the less the ionization energy of the atom. iv. Nature of Orbitals- There are four types of orbitals: s, p, d, and f. S orbital is more penetrating and the electron removal from this orbital is difficult. P orbital in the form of lobes and the electron removal from p orbital is easier. D orbital is easier than p orbital and it is easiest to remove electron from f orbital.

Factors affecting the electron affinities

i. Atomic Size-The greater the atomic size of the atom, the smaller the electron affinity ii. Nuclear Charge- Greater number of protons in the nucleus, greater the electron affinity iii. Shielding Effect- Greater shielding effect of inner levels, the lesser the electron affinity

Electrical conductance of IV-A elements

i. Carbon in the form of diamond is non-conductor, because all valence electrons are tetrahedrally bonded, and the cannot move freely. ii. Carbon in the form of graphite is a fairly good conductor of electricity. Anyhow, it shows anistropic behavior. Electrical current can pass parallel to the sheets. Actually loosely held electrons are availale parallel to the sheets for electrical conductivity iii.The lower elements of group IV-A like Sn and Pb are fairly good conductors.Their electrial conductivities are very close to the elements of Group I-A.

Benefits of Moseley's Law

i. Correct arrangement of some elements ii. Position of rare earths (of lanthanides and actinides was adjusted) iii. Position of isotopes- the isotopes of the same element possess the same atomic number. All of them should occupy the same place on the periodic table. iv. Placement of noble gases-noble gases were given a group number VIIIA/zero group. v. Position of coinage metals Cu, Ag, Au, Zn, Cd, and Hg were correctly placed.

Properties of Covalent Hydrides

i. Covalent hydrides are usually gases or volatile liquds ii Thy are soft and have low mp and bp iii. They are non-conductors of electricity iv. Some of them are soluble in organic solvents

Oxidation states of transition elements

i. Cu, Ag, Au are present in I-B, so their oxidationstates are +1, or +3 ii. Zn, Cd, Hg are presentin II-B, so their oxidation states are +2 iii. Cr has +6 oxidation state iv. Mn is present in VII-B and as +7 oxidation state

Oxidation number rules (4)

i. Elements of group I-A, which have one electron in the outermost shell show +1 oxidation state. They lose one electron from s-orbital. ii. Elements of group II-A which have two electron in the outermost shll show +2 oxidation state. They lose two electrons from s-orbital. iii. Elements of group III-A have oxidation state o +3 iv. Elements of group IV-A show oxidation state o +4

Oxidation number CAUTIOUS rules (4)

i. Elements of group V-A show two types of oxidation states: +5, and -3. ii. Elements of group VI-A show oxidation states of -2, +4, and +6. iii. The elements of group VII-A show -1, +3, +5,+7 as their oxidation states iv. The elements of group VIII-A show zero oxidation state.

Variation in metallic character in the periodic table

i. Metallic character increases from top to bottom in groups ii. Metallic character decreases from left to the right in a period iii. All the transition elements are metals and the metallic character increases from left to right up to the midde of the families, in d-block elements.

Defects of Mendeleev's Periodic Table

i. Position of Hydrogen-The properties of hydrogen resemble with alkali metals and halogens, but its position could not be decided by Mendeleev. ii. Idea about the structure of atom iii. Position of lanthanides and actinides- both do not find proper place in Periodic Table iv. Position of isotopes- Mendeleev's periodic table does not give any indication about position of isotopes. v. Dissimilar elements are placed together- Cu, Ag, Au differ from alkali metals yet the placed them together. vi. Cause of periodicity- Not clear

Advantages of Mendeleev's Periodic Table

i. Prediction of new elements- Mendeleev left some vacant spaces for those elements ii. Correction of atomic masses-Mendeleev was able to correct doubtful atomic masses.

Melting point and Boiling Point variation in groups (Reasons)

i. The binding forces present between large sized atoms ofgorup I-A, II-A, III-A, and IV-A are less. So their mp and bp are less. ii. In the case of lowr elements of group V-A, VI-A, VII-A, and zero grou elements, have greater polarizabilities so their mp and bp are higher.

Variation of electrical conductivity in periodic table

i. The elements of Group I-A, and II-A decrease their electrical conductivities from top to bottom in a group ii. The elements of group I-B (Cu, Ag, Au) are called coinage metals. They have highe levels of electrical conductance. iii. The elements of Group VI-A, VII-A, show very low electrical conductance.

Melting point and Boiling Point variation in periods (Reasons)

i. The elements of group I-A are alkali metals. They have only one electron in their outermost shells. They can make only one bond with other atoms. ii. The elements of group II-A have sufficiently high mp and bp than I-A. The reason is that each atom in thm provides two binding electrons. iii. Elements of group IV-A have highest mp and bp due to the presence of four electrons in their outermost orbital.

General properties of metals (5)

i. The elements which have a tendency to form positive ion by losing electrons are called metals. ii. They are good conductors of heat iii. They are good conductors of electricity iv. They are malleable and ductile v. They form basic oxides and produce bases with water

Gerneral properties of non-metals (3)

i. The elements, which have tendencies of forming negative ions by gaining electrons ii. They are not good conductors of heat and electricity iii. They give acidic oxides and give acids when dissolved in water.

Variation of hydrides in a period

i. The ionic character of the hydrides decrease from left to right ii. The stabilities of covalent hydrides increase from left to right iii. The possibility of formation of hyrogen bond increases from let t right. H bonding increases from CH4, NH3, to H2O to Hf

Variation of Hydrides in groups

i. The ionic charactr of the ionic hydrides increases down the group I-A and II-A ii. The stabilities of the covalent hydrides decrease from top to the bottom of a group iii. The boiling points of the covalent hydrides generally increase down the group

6 Features of Mendeleev's Periodic Law

i. The vertical columns were called groups ii. The horizontal rows were called periods iii. The arrangement was done according to increasing order of atomic masses. iv. The elements showing similar chemical properties appeared at regular intervals v. Some gaps were left in the table, not yet discovered vi. He predicted the properties of those elements which were yet to be discovered

General properties of metalloids (3)

i. Their electron losing and gaining capabilities are intermediate between metals and non-metals ii. Their electrical and thermal conductivities are between metals and non-metals iii. Their oxides are amphoteric, which means they can act as acidic and basic oxides

Essential features of groups

i. There are nine groups total, including group VIII of transition metals and the zero group of inert gases. ii. The group I to VII are subdivided into sub-groups A and B. iii. The elements of group I-A, II-A, etc. have their outermost shell incomplete, while each of their inner shell is complete. They are good metals. iv.

General Properties of Ionic Halides

i. They are hard crystalline substances like NaCLh ii. They have high mp and bp iii. They have 3D lattices consisting of discrete ions iv. They have lattice energie but the lattic energies of the fluorides are maximum, this is due to small size of F ion v. They are insoluble in organic solvens vi. They allow the electrical current to pass through them in the solution state and molten state vii. The order of mp and bp are as follows: metal fluorides> metal chlorides> metal bromides> metal iodides

General properties of Covalent Halides

i. They are mostly water soluble but less than those of ionic halides. ii. Some of these are gases, some are liquids an majority are solids iii. Their mp and bp are less than thos of ionic halide iv. Physical properties of covalent halides are influenced by the size an polarizability of the halogen atoms. v. Iodides have the largest sizes. They have greater polarizabilities. Greater van der waals forces higher the mp and bp than other covalent halides.

Melting point and Boiling Point variation in periods (Reasons)

iv. Carbon has highest mp and bp when it is in the form of a diamond. In diamond, each carbon is sp3 hybridized and four strong sigma bonds are produced with other atoms. v. The elements of group V-A, VI-A, and VII-A have low mp and bp because these elements exist in the form of diatomic molecules. There are least intermolecular forces and so their mp and bp are very low. So much that they exist as gases at room temperature.