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Flashcards in Chemistry definition Deck (47):
1

Isotopes:

Atoms, whose nuclei have the same atomic number (Z), but different mass number (A). (different neutron number.)

2

Principal quantum number:

Determine the distance from the nucleus. Identifies the shell.

3

Angular quantum number:

Determine the shape of the orbitals belonging to the subshell

4

Magnetic quantum number:

Orientation of the orbitals in magnetic field

5

Spin quantum number:

Refers the two possible orientation of the spin of an electron. Identifies the electron.

6

Pauli's exclusion principle:

No two electrons can have the same four quantum numbers in an atom.

7

Hund's rule:

(the rule of maximum multiplicity):

States that the electrons are distributed among the orbitals of a subshell in a way that gives the maximum number of unpaired electrons with parallel spins.

8

Building-up principle:

Means that the subshellsare built up in an order as the energy of the subshells increases (E n+ 0.7l).

9

Rules to determine the oxidation numbers:

1. The oxidation number of atoms in elements is zero.

2. 2. The oxidation number of alkali metals(column I. in periodic system)is always +1 (except elemental form).The oxidation number of alkali earth metals(column II. in periodic system) is always +2(except elemental form).The oxidation number of aluminiumis +3(except elemental).

3. 3. The oxidation number of hydrogen usually +1 (except elemental form) and hydrides, when it is -1 (e.g. LiH, CaH2, etc.). The oxidation number of oxygen usually is -2(except elemental form) and peroxides, when it is -1 (e.g. H2O2).

4. In molecules the algebraic sum of the oxidation numbers of atoms equals zero. In case of ions the sum of oxidation numbers equals the electrical charge of the ion.

10

Molar volume:

The molar volume (Vm) is the volume occupied by one mole of a substance (chemical element or chemical compound) at a given temperature and pressure.

11

Avogadro's law:

Equal volumes of all gases, at the same temperature and pressure, have the same number of molecules

12

The Lewis acid- base concept:

* Lewis-bases aremolecules or anions, that have lone electron pair(s)with which it can form covalent, dativebond (electronpair donors),
- e.g.ammonia, water, hydroxide ion, cyanide ion, halide ions, etc.

* Lewis-acids are molecules or cations that can form a covalent, dativebond by accepting an electron pair from a base (electron pair acceptors),
- e.g.boron trifluoride, proton, aluminum(III)ion, carbon dioxide, copper(II) ion, sulfur trioxide, etc.

13

Reaction rate:

Change in amount(or concentrationat const. volume) of a reactant or product in a given unit of time

14

Catalysts:

A catalyst is a substance that increases the rate of a chemical reaction without being used up in the reaction.
The catalyst, C:
- maybe recovered unchanged at the end of the reaction
- small amount is enough to accelerate a reaction -cannot initiate thermodynamically not allowed reactions

15

Ionization energy:

The amount of energy required to completely removing the most loosely held electron from the gaseous atom (units are: J, eV, or J/mol).

16

Bond order:

The half of the difference between the number of bonding-, and antibonding electrons in the given molecule. For O2: (10 – 6)/2 = 2

17

Isomerism:

Compounds having an identical composition and molecularmass, but different structure, and different physical andchemical properties

18

Constitutional isomerism:

Molecules having same molecular formula, but different order of atomic connections, are referred to as constitutional isomers. (Different structures with different properties)

19

Conformation:

Specific arrangement of atoms within a molecule, emerging from the free rotation around the C-C single bonds, is called conformation.

20

Cracking:

Transformation of high boiling hydrocarbons into simpler hydrocarbons of shorter carbon chain

21

Markovnikov's rule:

When an unsymmetrically substituted alkene reactswith a hydrogen halide, the hydrogen adds to the carbon that has greater number of hydrogen substituents.

22

Elimination:

The reaction that occurs when a single reactant splits apart into two products

23

Homogeneous equilibria:

All reacting componentsare in the same phase

24

Heterogeneous equilibria:

Equilibria between substances in two or more phases.

25

Le Chatelier- Braun principle:

A system in equilibrium reacts to a change (stress) in conditions in a way that counteractsthe applied change and establishes a new equilibrium state. Each change in the conditions (concentration, temperature, etc.) should be considered a stress.

26

Arrhenius concept:

* Acid: a compound that produces H+ ions in water

* Base: a compound that produces OH- ions in water

27

Brönsted- Lowry concept:

Acid, BH:
- A compoundthat can donate proton
(proton donor)

Base, B:
- A compoundthat can accept a proton
(proton acceptor)

28

Buffer solutions:

A buffer solution is capable of maintaining its pH at nearly constant value even whensmallamountsofstrongacidor-base are added.

29

Lewis concept:

Lewis-bases are molecules or ions, that have unshared electron pair(s)with which it can form covalent bond
(electron pair donors),
- e.g.ammonia, water, hydroxide ion, etc.

Lewis-acids are molecules or ions that can form a covalent bond by accepting an electron pair from a base
(electron pair acceptors),
- e.g.boron trifluoride, proton, aluminum(III)ion, carbon dioxide, copper(II) ion, etc.

30

Molality:

Quantity of substance B divided by mass of solvent. It is a temperature independent concentration. Its symbol is mB

31

Mass concentration:

The mass concentration of substance B divided by the volume of solution.

32

Mole fraction:

Quantity of substance B divided by the total quantity of matter in the solution.

33

Mass fraction:

Mass of substance B divided by mass of mixture.

34

Volume fraction:

Volume of substance B divided by volume of mixture.

35

Mass %:

g of solute in 100g of solution

36

Mol %:

Mol of solute in 100mol of solution.

37

Mixed %:

g of solute in 100cm3 solution

38

Ionization energy:

The amount of energy required to remove the most loosely held electron from an isolated atom in its ground state is called first ionization energy.

39

Electron affinity:

The energy change (E) associated with the process in which an electron is added to a gaseous atom in its ground state.

40

Electronegativity:

Is a chemical property that describes the tendency of an atom to attract electron density towards itself.

41

Lattice energy:

The energy required to convert the crystal into infinitely separated gaseous ions, in vacuum(an endothermic process).Unit: kJ/mol

42

Octet rule:

States that atoms of low atomic number tend to combine(with covalent or ionic bond)in such a way that they each have eight electrons in their valence shells, giving them the same electron configuration as a noble gas.

43

Stereoisomers:

Isomers that differ in spatial (three dimensional) arrangement of their atoms

44

Chiral molecule:

A molecule (or object) that is not superimposable on its mirror image is said to be chiral.

45

Enantiomers:

They are isomers differing only in the three-dimensional arrangement of substituents. These stereoisomers are called enantiomers. Enantiomers are mirror images that are not superimposable.

46

Optical activity:

Is the abiliity of a substance to rotate of the plane of polarized light

47

Diastereomers:

Are no mirror image isomers in general case:
- At least one chiral center should have the same configuration,

- At least one chiral center should have the opposite configuration