- Continuing on…This article contains revision note out of Chapter 3, 4 and 5 of Chemistry Class11.
- Chapter 4 mostly ignored because it deals with Chemical Bonding And Molecular Structure, The valence bond (VB) approach, The VSEPR model, molecular orbital (MO) theory and other technical things.
Metals vs. Non-metals vs. Metalloid
- Metals comprise more than 78% of all known elements
- They appear on the left side of the Periodic Table
- located at the top right hand side of the Periodic Table.
- the non- metallic character increases as one goes from left to right across the Periodic Table
|usually solids at room temperature [mercury is an exception; gallium and caesium also have very low melting points (303K and 302K, respectively)].
||Non-metals are usually solids or gases at room temperature with low melting and boiling points (boron and carbon are exceptions)
|Have high melting and boiling points.
|Good conductors of heat and electricity.
|malleable: can be flattened into thin sheets by hammering
|ductile: can be drawn into wires
Semi-metals or Metalloids: silicon, germanium, arsenic, antimony and tellurium show properties that are characteristic of both metals and non- metals.
- Liquids have definite volume because molecules do not separate from each other.
- Liquids can flow, they can be poured, because their Molecules can move past one another freely.
- Liquids can assume the shape of the container in which these are stored.
- Liquids may be considered as continuation of gas phase into a region of small volume and very strong molecular attractions.
- Physical properties of liquid = (1) vapour pressure (2) surface tension (3) viscosity. These are due to strong intermolecular attractive forces.
Liquids: Vapour Pressure
- liquid evaporates and pressure exerted by vapour on the walls of the container (vapour pressure)
- The normal boiling point of water is 100 °C (373 K), its standard boiling point is 99.6 °C (372.6 K).
- Standard boiling point of the liquid is slightly lower than the normal boiling point because 1 bar pressure is slightly less than 1 atm pressure.
- Liquids at high altitudes boil at lower temperatures in comparison to that at sea level, because at high altitudes atmospheric pressure is low. (important for assertion-reasoning)
- In hills, water boils at low temperature therefore, Pressure cooker is used for cooking food.
- In hospitals surgical instruments are sterilized in autoclaves. Autoclaves increase the boiling point of water by increasing the pressure above the atmospheric pressure by using a weight covering the vent.
- Boiling does not occur when liquid is heated in a closed vessel.
Liquid: UPSC Surface Tension
Surface tension is responsible for following events (important for MCQ):
- Small drops of mercury form spherical bead instead of spreading on the surface.
- Particles of soil at the bottom of river remain separated but they stick together when taken out.
- Liquid rise (or fall) in a thin capillary as soon as the capillary touches the surface of the liquid.
- On flat surface, droplets are slightly flattened by the effect of gravity; but in the gravity free environments, the liquid drops will be perfectly spherical.
Principle: Liquids tend to minimize their surface area. Surface tension denoted by Gamma, its SI unit NM-1
Liquids: Viscosity & Laminar flow
- Viscosity is a measure of resistance to flow which arises due to the internal friction between layers of fluid
- SI unit of viscosity coefficient= 1 newton second per square metre = pascal second
- CGS unit of viscosity coefficient = Poise (named after great scientist Jean Louise Poiseuille).
- Greater the viscosity, the more slowly the liquid flows.
- Viscosity of liquids decreases as the temperature rises.
- Glass is an extremely viscous liquid- so viscous that many of its properties resemble solids.
- Windowpanes of old buildings- they become thicker at bottom than at top. This is because of liquid flow property of glass.
- Laminar flow is type of flow in which there is a regular gradation of velocity in passing from one layer to the next.
- Gases are highly compressible
- Gases exert pressure equally in all directions.
- Gases have much lower density than the solids and liquids.
- Gases can assume volume and shape of the container. Their volume and the shape of gases are not fixed.
- Under suitable temperature and pressure conditions gases can be liquified
- Gases mix evenly and completely in all proportions without any mechanical aid.
- The noble gases exhibit very low chemical reactivity because all of their orbitals completely filled by electrons. Very difficult to add/remove electrons from it. (Example: helium, neon, argon, krypton, xenon, radon, and element 118)
- 11 elements exist as gases.
- first reliable measurement on properties of gases (1662)
- Boyle’s Law (Pressure – Volume Relationship)
- at constant temperature, the pressure of a fixed amount (i.e., number of moles n) of gas varies inversely with its volume.
- P1V1=P2V2= constant
- Gases are highly compressible because when a given mass of a gas is compressed, the same number of molecules occupy a smaller space
- This means that gases become denser at high pressure.
- Temperature – Volume Relationship
- At constant pressure, volume of a gas increases on increasing temperature and decreases on cooling. (V = k2T )
- This new temperature scale is called the Kelvin temperature scale or Absolute temperature scale.
- Kelvin scale of temperature is also called Thermodynamic scale of temperature and is used in all scientific works.
- Each line of the volume vs temperature graph is called isobar.
- The lowest imaginary temperature at which gases are supposed to occupy zero volume is called Absolute zero.
- All gases obey Charles’ law at very low pressures and high temperatures
|Gay Lussac’s Law
- Pressure- Temperature Relationship
- Pressure in well inflated tyres of automobiles is almost constant, but on a hot summer day this increases considerably and tyre may burst if pressure is not adjusted properly.
- During winters, on a cold morning one may find the pressure in the tyres of a vehicle decreased considerably.
- At constant volume, pressure of a fixed amount of a gas varies directly with the temperature. Mathematically. P/T = constant.
- This relationship can be derived from Boyle’s law and Charles’ Law.
- Pressure vs temperature (Kelvin) graph Each line of this graph is called isochore.
|Avogadro Law,Italy, 1811
||Volume – Amount RelationshipEqual volumes of all gases under the same conditions of temperature and pressure contain equal number of molecules.As long as the temperature and pressure remain constant, the volume depends upon number of molecules of the gas V=k4n.
- Standard temperature and pressure means 273.15 K (0°C) temperature and 1 bar (i.e., exactly 105 pascal) pressure.
- These values approximate freezing temperature of water and atmospheric pressure at sea level.
|Dalton Partial pressure, 1801
- Total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases
- In a mixture of gases, the pressure exerted by the individual gas is called partial pressure.
- pTotal = p1 +p2 +p3 +…..
- At 30.98 C carbon dioxide remains gas upto 73 atmospheric pressure. At 73 atmospheric pressure, liquid carbon dioxide appears. Therefore, 30.98 C is called critical temperature of carbon dioxide. Because this is the highest temperature at which liquid carbon dioxide is observed.
- A gas below the critical temperature can be liquefied by applying pressure, and is called vapour of the substance.
Ideal Gas vs. Real gas
|Ideal gas follows Boyle’s law, Charles’ law and Avogadro law strictly-at all temperature and pressures.
||They do not follow, Boyle’s law, Charles law and Avogadro law perfectly under all conditions.
|Ideal gas equation: pV=nRT is applicable to them
|Such a gas is hypothetical, it goes on assumption that intermolecular forces present in an ideal gas.
||Their molecules interact with each other.
- Boyle temperature: At this temperature real gas obeys ideal gas law.
- This Boyle point/temperature of a gas depends upon its nature.
|Johann Dobereiner (German)
|AEB De Chancourtois (French)
|Lothar Meyer (German)
||His table closely resembles the Modern Periodic Table. But his work published after Mendeleev. Therefore, Mendeleev credited with Modern Periodic Table.
Mendeleev’s table: Characteristics
- Russian Chemist Mandeleev (1834-1907) wrote famous textbook “Principles of Chemistry”
- Modern Periodic based on 3 principles: (1) physical and chemical properties of the elements are periodic functions of their atomic numbers. (2) aufbau (build up) principle (3) Electronic configuration of atoms provide a theoretical foundation for the periodic classification.
- He arranged elements in horizontal rows (periods- in increasing atomic weights.)
- And vertical columns (groups- they’ve same electron configuration in outer orbit).
- The elements with similar properties occupied the same vertical column or group.
- Left gaps for the elements that were not found in his time, predicted the elements that were yet to be found.
- Element with atomic number 101, as Mendelevium- is named in honor of this scientist.
- If new element discovered, its permanent name and symbol are given by a vote of IUPAC representatives from each country.
- As per IUPAC note, latest element is 118 but its credit yet to be given.
- Chemical reactivity is highest at the two extremes of a period and is lowest in the centre.
- Highly reactive elements do not occur in nature in Free State; they usually occur in the combined form.
- Oxides of elements on left are basic
- Oxides of elements on the right are acidic
- Oxides of elements in the centre are amphoteric or neutral.
We can classify the elements into four blocks depending on the type of atomic orbitals that are being filled with electrons
||Group 1 (alkali metals) and Group 2 (alkaline earth metals)
||Representative Elements or Main Group Elements
- Transition Elements.
- They mostly form coloured ions
- they display paramagnetism (i.e. attracted by magnetic field)
- They are used as catalysts
- Inner-Transition Elements
- They are all metals.
- located in bottom two rows of the table.
- two rows of elements at the bottom of the Periodic Table, called the Lanthanoids and Actinoids,
- Actinoid elements are radioactive.
- Most actinoid elements found only in nanogram quantities during nuclear reactions and their chemistry is not fully studied.
- The elements after uranium are called Transuranium Elements.
Cation vs Anion
|removal of an electron from an atom leads to cation
||Gain of an electron leads to an anion.non-metals have strong tendency to gain electrons.
|Smaller than parent atom, because less electrons.
||Larger than parent atom.
- Which of the following metals exist as liquid?
- Find correct statements about (1) metal (2) Non-metal (3) Metalloid (4) Gases (5) ideal gas (6) Modern Periodic table
- Which of the following events are caused by surface tension?
- Viscosity depends on which of the following factors?
- Match the following: scientist vs. gas law, block-element vs characteristic
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