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1. wk > Atoms, Mol, a Matter > Flashcards

Atoms, Mol, a Matter Flashcards

1
Q

Describe the ancient view towards matter

A
  • Matter: any substance which has mass and occupies space
  • Empedeocles argued that all matter was composed of four elements: fire, air, water, and earth. The ratio of these four elements affected the properties of the matter.
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2
Q

Was was Democritus’s theory?

A
  • 460 b.c. to 370 b.c

- infinitesimally (unendlich) small pieces of matter, atomos, meaning “indivisible” or “uncuttable”

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3
Q

Define atom, element, and molecule

A

-Atom:
The smallest particle of an element that has all the element’s chemical properties. The smallest particle that retains its chemical identity
-Element:
A fundamental or elementary substance that cannot be broken down by chemical means to simpler substances. Atoms of one kind form a chemical element
-Molecule:
The smallest physical unit of an element or compound, consisting of one or more like atoms in an element and two or more different atoms in a compound

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4
Q

What can be said about chemical elements? (how many are found/ variety?)

A
  • great variety of substances but not great variety of atoms
  • > variety results from the many ways a few types of atoms can be combined
  • 118 elements
  • 94 are found naturally
  • 24 are synthetic elements,
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5
Q

What did Dimitri Mendeleev in Russia (1869) and Lothar Meyer in Germany (1870) recognize?

A
  • there was a periodic relationship among the properties of the elements known at that time
  • but Mendeleev used his table to predict the existence of unknown elements

((-elements can be grouped according to their similar chemical behaviors)

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6
Q

Define compounds and molecules

A
  • Compounds: substances formed by the chemical combination of two or more atoms of the elements. A single “particle” of a compound is called a molecule
  • Molecule: The smallest particle of an element or compound that retains the chemical properties of the element or compound. A collection of chemically bound atoms with characteristic composition and structure
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7
Q

How much does H2 make over the atoms in the known universe?

A

-over 90%

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8
Q

Where are elements heavier than H2 manufactured?

A

-in the deep interior of stars

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9
Q

Which elements compose more than 99% of the earth?

A
  • H, C, N, O, Na, Mg, Al, Si, P, S, Cl, K, Ca, Fe )

- > the majority of elements are relatively rare

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10
Q

Which elements primarily compose living things?

A

-O, C, H, N and Ca; smaller role P and S

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11
Q

What is the Brownian motion?

A

-the haphazard movement of tiny particles suspended in a gas or liquid resulting from bombardment by the fast-moving molecules of the gas or liquid
(the spores of pollen under a microscope)

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12
Q

What did Albert Einstein published in 1905?

A
  • several papers that explained how Brownian motion could be used to measure the size of atoms and molecules
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13
Q

What did Jean Baptiste produce?

A
  • produced accurate sizes for atoms and molecules using Einstein’s ideas and his observations
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14
Q

What is Graphene?

A

-Graphene is one of the strongest, lightest and most conductive materials known to humankind

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15
Q

Describe the modern atomic Theory by Dalton Model?

A
  • For each chemical element there was a corresponding (entsprechende) species of indivisible objects called atoms.
  • Indivisible atoms provided the fundamental building blocks of all matter.
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16
Q

How do atoms differ from each other? Atoms combine to form what? What does a chemical reaction involve? How do elements react to form compounds?

A
  • All atoms of a given element are identical; atoms of different elements have different properties
  • form molecules that in turn combine to form the compounds and substances of matter
  • the combination of atoms, not the destruction of atoms
  • they react in defined, whole number ratios
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17
Q

Describe The Plum Pudding Model (From where does the name came?)

A
  • J.J.THOMSON (1856-1940)identified the electron using a cathode ray tube(CRT) (A CRT is a specialized vacuumtube in which images are produced when an electron beam strikes aphosphorescent surface)
  • In his model, small negatively charged electrons were scattered around the entire atom, more or less like raisins in a bun (cake)
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18
Q

How was Rutherford’s experiment designed?

A
  • beam of positively charged α-particles (like tiny subatomic bullets!) from a radioactive source through a very thin gold leaf
  • They measured the angles at which the α-particles were deflected from their straight–line path as they emerged from the gold foil
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19
Q

What was the aim of the experiment (Rutherford) ?

A

-to measure something about the ways atoms were put together

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20
Q

The observation of the experiment

A
  • Almost all the alpha particles either passed right through the gold foil unaffected or were scattered through very small angles
  • One particle in a thousand was scattered through a large angle; some even bounced straight back
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21
Q

What did his (Rutherfords) experiment show? How does his model look like and what are the problems related to his model?

A
  • This experiment showed that the atom was mostly empty space, with most of its mass packed into the central region: the nucleus
  • A small dense , positively charged nucleus w/light, negatively charged electrons circling it, like planets orbiting the Sun.
  • an object traveling in a circular orbit is constantly being accelerated ; and any accelerated electric charge must give off electromagnetic radiation, as a result of Maxwell’s equations
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22
Q

What was Rutherfords model missing to explain?

A

-Rutherford’s model could not explain why negatively charged electrons remain in orbit, when they should instantly fall into the positively charged nucleus

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23
Q

What does the Bohr planetary model describe?

A
  • Hydrogen gas glows by giving off light in several separate wavelengths rather than in a continuous range
  • Only certain “allowed” orbits, in which an electron could exist without giving off radiation
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24
Q

How is photon emitted (ausgesendet)?

A

-Photon, particle-like bundle of light emitted when an e moves from an upper state to a lower state

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25
Q

What happens if a light (emitted by a gas) is passed through a prism?

A

-When light emitted by a gas is passed through a prism a set of brightly colored lines results

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26
Q

Light and the relation to wavelengths?

A

-Light is being emitted only at certain wavelengths that correspond to specific colors

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27
Q

Describe the Bohr Model of the atom

A
  • the electron travels in circular orbits around the nucleus
  • the orbits have quantized sizes and energies
  • energy is emitted from the atom when the electron jumps from one orbit to another closer to the nucleus
28
Q

What is the problem with the Bohr model?

A
  • It violates the Heisenberg Uncertainty Principle (that the position and the velocity (Position) of an object cannot both be measured exactly, at the same time, even in theory) because it considers electrons to have both a known radius and orbit (Umlaufbahn)
29
Q

Describe the electron cloud model (1920s)

A
  • Erwin Schrodinger and Werner Heisenberg
  • An atom consists of a dense nucleus composed of protons and neutrons surrounded by electrons that exist in different clouds at the various energy levels.
30
Q

What is an orbital, principal quantum number? To what are electrons restricted?

A

-Orbital: a region in space around the nucleus where there is a high probability of finding an electron
-Electron restricted to only certain allowed energies: principal energy levels
(Hauptenergieniveaus)
-the principal quantum number (n): the size of the orbital
->The principal quantum number indirectly describes the energy of an orbital

31
Q

How are the energy levels calculated?

A

-En= -13,6 eV / n^2

32
Q

What does the angular quantum number describe? Describe the different kinds

A
  • The angular quantum number (l) describes the shape of the orbital (the space where there is a 90% probability that the electron may be found)
  • spherical (l = 0; s state), polar (l = 1; p state), or cloverleaf (kleeblatt) (l = 2; d state)
  • > It determines the electron’s kinetic energy due to its angular momentum
33
Q

What does the magnetic quantum number describe?

A

-The magnetic quantum number (m), to describe the orientation in space of a particular orbital

34
Q

What does the spin quantum number show?

A
  • whether they either (behave as) rotate(ing) in a clockwise or counterclockwise fashion (Specifies the orientation of the spin axis of an electron )
  • +1/2 means counterclockwise
  • -1/2 means clockwise
35
Q

What do the electron generate while spinning?

A

-magnetic field

36
Q

Which numbers are the electrons in an orbital assigned?

A

-an s quantum number of +1/2, the other is assigned an s quantum number of -1/2

37
Q

Name the rules for quantum numbers

A

-The three quantum numbers (n, l, and m) that describe an orbital are integers (ganze Zahlen): 0, 1, 2, 3, and so on.
The principal quantum number (n) cannot be zero. The allowed values of n are therefore 1, 2, 3, 4, and so on.
The angular quantum number (l) can be any integer between 0 and n - 1. If n = 3, for example, l can be either 0, 1, or 2.
The magnetic quantum number (m) can be any integer between -l and +l. If l = 2, m can be either -2, -1, 0, +1, or +2

38
Q

What is the Pauli exclusion principle?

A

-The Pauli exclusion principle (Wolfgang Pauli, Nobel Prize 1945) states that no two electrons in the same atom can have identical values for all four of their quantum numbers

39
Q

Give the evolution of atomic theory (in short)

A 
-marble (Dalton- 1803)
 pudding (Thompson- 1904)
nuclear (Rutherford- 1911) 
planetary (Bohr- 1913) 
quantum wave function (Schrodinger- 1926)
40
Q

Which bondings are in noncovalent bonds included?

A
  • The Hydrogen Bond
  • Ionic Interactions
  • London-Van der Waals
  • Interactions
  • Hydrophobic Bonds
41
Q

What are covalent bonds?

A
  • Bond in which one or more pairs of electrons are shared by two atoms
  • Difference in the electronegativities is quite small.
  • Relatively high energies are required to break them (50–200 kcal/mol)
  • ex: H2, F2, CO2, CF4
42
Q

What are ionic bonds?

A 
-Bond in which one or more
electrons from one atom are
removed and attached to 
another atom, resulting in 
positive and negative ions 
which attract each other
-1. "atoms" - electron transfer - "ions"-  electrostatic attraction - "ionic bond"
43
Q

What is electronegativity?

A 
-The ability of an atom to 
attract electrons in the 
presence of another atom
is a measurable property 
called electronegativity
44
Q

What is the Coulomb’s law formula ?

A

-F=k q1.q2/ r2

45
Q

Which forces are the London- van Der Waals forces?

A
  • Dipole-Dipole Forces
  • Dipole-Induced Dipole Forces
  • Induced Dipole-Induced Dipole Forces
46
Q

Define the dipole- dipole force

A
  • the difference between the electronegativities of the atoms in these molecules is large enough that the electrons aren’t shared equally, and yet small enough that the electrons aren’t drawn exclusively to one of the atoms to form positive and negative ions
  • The bonds in these molecules are said to be polar, because they have positive and negative ends, or poles, and the molecules are often said to have a dipole moment
47
Q

Compare dipole- dipole interaction with covalent bonds

A

-The dipole-dipole interaction in HCl is relatively weak; only 3.3 kJ/mol. (The covalent bonds between the hydrogen and chlorine atoms in HCl are 130 times as strong.)

48
Q

define dipole- induced dipole forces

A
  • Dipole-Induced Dipole Forces
  • By distorting the distribution of electrons around the argon atom, the polar HCl molecule induces a small dipole moment on this atom, which creates a weak dipole-induced dipole force of attraction between the HCl molecule and the Ar atom. This force is very weak, with a bond energy of about 1 kJ/mol
49
Q

define induced dipole induced forces

A

-These fluctuations (Schwankungen) in electron density occur constantly, creating an induced dipole-induced dipole force of attraction between pairs of atoms. As might be expected, this force is relatively weak in helium – only 0.076 kJ/mol. ->But atoms or molecules become more polarizable as they become larger because there are more electrons to be polarized

50
Q

Define the hydrogen bond

A
  • It is a force of attraction between a hydrogen atom in one molecule and a small atom of high electronegativity in another molecule
  • Usually the electronegative atom is oxygen, nitrogen, or fluorine, which has a partial negative charge. The hydrogen then has the partial positive charge.
51
Q

Compare hydrogen bond with covalent bond

A

-This attraction or “hydrogen bond” can have about 5% to 10% of the strength of a covalent bond.

52
Q

Define hydrophobic bonds (interactions)

A
  • The tendency of hydrocarbons (Compounds that contain only carbon and hydrogen) (or of lipophilic hydrocarbon-like groups in solutes) to form intermolecular aggregates in an aqueous medium, and analogous intramolecular interactions.
  • > attraction is actually caused by a repulsion (Abstoßung) from water
53
Q

Give the bond strength of covalent, ionic, van Der Waals, hydrogen, hydrophobic

A
  • covalent = 50-1000 kcal/mole
  • ionic= 5 (aq); >= 100 (crystal)
  • van der Waals= 1-2
  • hydrogen= 3-7
  • hydrophobic= 3-4
54
Q

Intermolecular energy related with distance

A
  • As the molecules move closer together, the energy decreases if the molecules attract each other, until it is minimal at an optimal interaction distance
  • The atoms in the two molecules begin to collide at shorter distances and the energy goes up sharply
55
Q

How can the energy of interaction between two molecules calculated?

A
  • by summing up the interaction energies between pair-wise combinations of atoms in the two molecules.
56
Q

Describe the van der Waals attractions (London forces) btw two neutral atoms

A

-When two neutral atoms approach each other, the electron clouds of the two atoms are polarized, which means that the electrons become redistributed (neu verteilt) so as to produce a dipole moment in the atom. Such dipoles attract each other, but the charge polarization is transient

57
Q

Name the electronegativity and van der Waals radius of: O, Cl, N, S, C, P, H

A
  • O= E(3,4); °A (1.5)
  • Cl= 3,2; 1,9
  • N= 3.0; 1,6
  • S= 2,6; 1,8
  • C= 2,6; 1,7
  • P= 2,2; 1,8
  • H=2,1; 1,2
58
Q

How is. the interaction between two oppositely charged groups called?

A

-a salt bridge or ion pair
-such as combination between arginine (pos charged amino acid)
and glutamate (negatively charged amino acid)

59
Q

How much greater is the electrostatic energy than van der Waals?

A

-typically 10-100 times

60
Q

What kind of influence does water have on ionic strength?

A

-water attenuates (dämpfen) it
-in vaccum around 500kJ / mol
-in water around 6kJ/ mol
-protein interior (inner side)
250kJ/ mol
-preotein surface (around is water) 20kJ/ mol

61
Q

How can hydrogen bonds else formed?

A

-due to induced dipoles

62
Q

When are the hydrogen bonds only favorable?

A

-in close contact

63
Q

Are the molecules which contain aromatic rung systems polarized?

A

-Molecules that contain aromatic ring systems, such as the phenylalanine and tyrosine side chains of proteins and the bases of nucleic acids, are polarized

64
Q

What drives the nucleic acid folding? (bonds)

A

-The energetics of van der Waals attractions and base stacking

65
Q

Oil and water do not mix, why?

A

-Hydrophobic effect
-Hydrophobic molecules come together to minimize the collective surface area that is exposed to water, with which these molecules cannot interact favorably
->
The hydrophobic effect is the most important determinant of protein structure.

1. wk (11 decks)

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