LAWS AND PRINCIPLES

                                              LAWS AND PRINCIPLES

Aufbau principle: - when building up atoms one proton is added at a time to the nucleus and one electron around it to obtain the ground state electron configuration of the element.  

AVOGADRO’S LAW: - States that equal volume of all gases at the same temperature and pressure contain the same number of molecules

BOYLE’S LAW: - States that the volume of a given mass of gas is inversely proportional to its pressure provided the temperature remains constant.

Mathematically   Vἀ1/P       T= constant

CHARLES LAW: - States that the volume of a given mass of gas is directly proportional to it temperature provided the pressure remains constant. 

Mathematically   V ἀ T         P=constant

COLLISION THEORY: - This theory assumes that for a chemical reaction to occur, there must be effective collision between reactants particles 

COULOUMB’S LAW: - state stat the electrostatic force associated with two charges A and B is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them

DALTON’S ATOMIC THEORY: - States that 

I.      All element is made up of small indivisible particles called atoms

II.    Atoms can neither be created nor destroyed during the cause of a chemical reaction to 

III.   Atoms of a particular element are exactly alike in all respect but are different from atoms of other              elements.

IV.   When atoms combine together, they do so in simple whole number ratio to one another 

DALTON’S LAW OF PARTIAL PRESSURE: - of partial pressure; states the in a mixture of gases that do not react chemically together, the total pressure exerted by the gas is the sum of the individual gases that make up the mixture.

P_TOTAL =P₁ +P₂+P₃+.......+P_n

FARADAY’S FIRST LAW OF ELECTROLYSIS: - States that the mass of an element deposited or liberated at an electrode during electrolysis is directly proportional to the quantity of electricity passing through the electrolyte.

 Mathematically m ἀ Q

FARADAY’S SECOND LAW OF ELECTROLYSIS: - states that if the same quantity of electricity is passed through solutions of different electrolyte the number of moles of each element discharged is inversely proportional to the charge on the ion

GAY –LUSSACS LAW of combining volume: - state that when gases combine, they do so in volumes which are in simple ratio to one another and to the volume of the product if gaseous provided temperature and pressure remain constant.

GRAHAM’S LAW OF DIFFUSION: - States that the rate of diffuse on of a gas is inversely proportional to the square root of its vapour density provided temperature and pressure remains constant.

HESS’S LAW OF CONSTANT HEAT OF SUMMATION: - This law states that the total enthalpy change of a chemical reaction is constant regardless of the route by which the chemical change occurs, provided that the conditions at the start of a reaction are the same as the final conditions

HUND’S RULE of maximum multiplicity: - state that when electrons fill degenerate orbitals they go in singly first before pairing occurs.

LE’CHATERLIER’S PRINCIPLE: - states that if an external constraint (such as a change in temperature, pressure or concentration) is imposed on a system in equilibrium the equilibrium will shift so as to cancel /annul the effect of the change.

LAW OF CONSERVATION OF MASS: - State that mater can neither be created nor destroyed but can be converted from one form to another.

LAW OF CONSTANT COMPOSITION: - States that all pure samples of a given chemical compound contain the same element combined in the same proportion by mass.

LAW OF DEFINITE PROPORTION: -See law of constant composition

LAW OF MULTIPLE PROPORTIONS: - States that if two elements A and B combine to form more than one compound, the various masses of A that combines with a fixed mass of B are in simple ratio with one another

MARKOVNIKOFF'S RULE: - states that when a hydrogen halide is adding to an already substituted alkene, the hydrogen atom from the halide will attach itself to the Carbon atom with the highest number of hydrogen atoms.

PAULI’S EXCLUSSION PRINCIPLE: - This principles states that 'No two electrons in the same orbital of an atom should have the same set of four quantum numbers'.

DEFINITIONS IN CHEMISTRY

DEFINITION

AN ACID

Arrhenius definition: An acid is a substance which produces hydrogen ion (H⁺) as the only positive ion in solution.

                                   HCl  → H+  +  Cl-

                                    H2O → H+  + OH-

Bronsted -Lowry’s definition: An acid is a proton donor.

Lewis's acid: An acid is any species that accepts an electron pair.

ACID-ANHYDRIDE: is the oxide of a nonmetal which dissolves in water to yield the corresponding acid.

ABSOLUTE-ZERO-TEMPERATURE: This is the lowest temperature in the Kelvin scale in which the volume of a gas is assumed to be zero.

ACTINADES: The Period 7 elements that forms the second inner transition series (5f block). It includes thorium (Th;Z=90) through lawrencium (Lr; Z=103) 

ACTIVATED COMPLEX: It is the highest energy level in a chemical reaction where the reactants are no longer reactants but are not yet products.

ACTIVATION ENERGY: this is the minimum amount of energy reactant particles must possess before a chemical reaction can occur.    OR it is the energy barrier that reactants must overcome to become products

ACTIVITY: The change in number of nuclei (N) of a radioactive sample divided by the change in time (t)

ALKANES: A hydrocarbon with the general molecular formular CnH2n+2. having only C-C single bonds

ALKENES: A hydrocarbon that contains at least one  carbon-carbon double bond (C=C bond)with the general formula CnH₂n.

ALKYNES: A hydrocarbon that contains at least one carbon-carbon triple bond (C=C ) with general formula CnH_2n-2

ALLOTROPY: This is  when an element occurs in different form but in the same physical state.

ALLOTROPES: These are different forms of an element occurring in the same physical state.

ALPHA (Ἀ) DECAY:  A radioactive process in which an alpha particle is emitted from the  nucleus of a radioactive element.

ALPHA  PARTICLE (ἀ or ⁴₂He).  A  positively charged particle, identical to a helium nucleus.

ANION: A negatively charged ion e.g  Cl^-, O^2-, N^3- .

ANODE: The electrode at which oxidation occurs in an electrochemical cell or an electrolytic cell.

ATOM: this is the smallest particle of an element that can take part in a chemical reaction.

ATOMIC MASS: This is the sum of the protons and neutrons in an atom of an element.

ATOMIC NUMBER: This is the number of protons in one atom an element.

BETA (β) DECAY: This involves the emission of a beta particle by a radioactive isotope.

BOILING POINT OF A LIQUID -: This is the temperature at which the saturated vapour pressure of the liquid is equal to the atmospheric pressure.

CATALYST: This is a substance that alters the rate of a chemical reaction, but itself is not affected by the reaction. 

CARBOHYDRATES:- These are organic compounds that contain carbon, hydrogen and oxygen, where     the hydrogen and oxygen are in the ratio of 2:1

CATHODE :- this is the electrode where reduction occurs in an electrochemical cell or an electrolytic cell.

CHEMICAL CHANGE: this is a change that is not easily reversible and in which a new substance is formed.

CONCENTRATION: this is the amount of a solute in moles per dm³ of   solution.  

COMBINATION REACTION: This is when two or more elements  combine  together to form a single compound       example        

                                     Fe_{(s) +}  S_(s) → FeS_(s)

COVALENT BONDING: this is a type of bonding that involves the sharing of electron pair between two atoms ( usually non-metals)

Cracking: this is the breaking down of higher molecular mass alkanes to lower molecular mass alkanes and alkenes.

   C₁₀H₂₂  → C8H18 +  C2H4

DEGENERATE ORBITALS: These are orbitals that are at the same energy level examples include the  p-orbital, the d-orbital and the f-orbital.

EFFLORESCENCE: this is the phenomenon whereby some salts when exposed to the atmosphere loses part or all of their water of crystallization.

EFFLORECENT SALTS; these are salts which loses part or all of their wate of crystallization when exposed to the atmosphere.

ELECTRON AFFINITY: This is the energy evolved when an electron enters an atom in the gaseous state to form a mole of gaseous negative ions.

ELECTROLYSIS: - This is the decomposition of a compound brought about by the passage of a direct current through either a solution of the compound or its molten form 

ELECTRONEGATIVITY:  Is defined as the power of an atom to attract (shared pair or bonded) electrons in a molecule.

ELECTROVALENT BOND: this is a type of bond that involves the transfer of electrons from one atom (metal) to another (non-metal).           OR             

 it is the electrostatic force of attraction between oppositely charged ions / cations and anions.

EMPIRICAL FORMULA: - This is the simplest formula of a compound; it shows the elements present and the ratio to which they are combined.

ENDOTHERMIC REACTION: This is a reaction during which heat is absorbed from the  surrounding.

END POINT: This is the point at which the chemical reaction is complete during titration. The end point is detected with the help of an indicator.

ENTHALPY: This is the total heat content of a body/substance 

ENTROPY:- This the degree of disorder or randomness of a system.

ESTERIFICATION REACTION: This is the reaction between an alkanoic acid and an alkanol to form an alkanoate (ester) and water only. 

  RCOOH + R'OH  → RCOOR' + H2O

EXOTHERMIC REACTION: This is a reaction during which heat is given off to the surrounding.

FERMENTATION:- This is the breakdown of carbohydrates into ethanol and carbon (IV) oxide by the action of micro-organism.

FUNCTIONAL GROUP: - A functional group may be a bond, an atom or a radical it is common to a homologous series and it  also determines the  chemical property of the series.

HALF-LIFE: - This is the time taken for half the total number of atoms in a given sample of a radioactive substance to undergo decay.

HOMOLOGOUS SERIES: - This is a family of organic compounds that have a regular structural pattern where successive members differs by a -CH2- group.

HYBRIDIZATION:- This is mixing of two or more orbitals to form a set of new and equal number of hybrid orbitals.  the three most common types of hybridization are the sp3, the sp2 and the sp hybridization

HYGROSCOPY: This is a phenomenon whereby some substances when exposed to the atmosphere absorbs moisture and only become sticky or wet.

ION: This is a charged atom (particle) or group of atoms carrying a charged.

IONISATION ENERGY: - This is the energy required to remove an electron from an atom to form a mole of gaseous ions.

IONIC BOND: see electrovalent bond.

ISOMERS: these are organic compounds with the same molecular formula but different structural formula.

ISOMERISM: This is the occurrence of two or more organic compounds with the same molecular formula but different structural formula.

ISOTOPES: These are atoms of the same element with the same atomic number but different mass number.

ISOTOPY: This is the occurrence of atoms of the same element with the same atomic number but different mass number. 

MASS CONCENTRATION: This is the concentration expressed in g/dm3

MOLAR CONCENTRATION: This is the concentration expressed in mols/dm3

MOLAR MASS: - This is the mass of one mole of a substance. the unit is g/mol.

MOLAR SOLUTION: These is a solution that contains one mole (1mol) or the molar mass of a substance in 1dm3 of solution

MOLECULAR FORMULA: -This is the actual formula of a compound; it shows the exact number of atoms present in one molecule of compound.

OXYDATION: This is the loss of electrons from a substance.

OXYDIXING AGENT: A substance that accepts/gains electrons.

PHYSICAL CHANGE: this is a change that is easily reversible and in which no new substance is formed.

POLLUTION:- This is the release of harmful substances into the atmosphere  in concentration that is harmful to man and his environment.

POLYMERIZATION: This is the process whereby two or more small molecules (monomers) link together to form large molecules (polymer).

REDUCTION: This is the gain of electrons 

REDUCING AGENT: A substance that donate/loss electrons 

SATURATED SOLUTION: - This is a solution that contains as much solute particles as it can hold at a particular temperature in the presence of undissolved solute particles.

STANDARD SOLUTION: This is a solution with a known concentration.  

SUPER SATURATED SOLUTION: - This is a solution that contains More than the solute it can normally hold a particular temperature.

SOLUBILITY: - Solubility of a solute in a solvent is the amount of solute in moles or grams that can saturate 1dm3 of solvent (water) at a particular temperature.