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MCAT > 4E: Atoms, nuclear decay, electronic structure, and atomic chemical behavior > Flashcards

4E: Atoms, nuclear decay, electronic structure, and atomic chemical behavior Flashcards

1
Q

atomic # (Z)

A

of protons in a nucleus and also # of electrons in neutral atom

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2
Q

isotopes

A

atoms of a single element (same Z) that differ in # of neutrons in their nuclei (diff masses)

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3
Q

atomic mass

A

aka amu, is the avg mass of all the isotopes of an element

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4
Q

1 amu in g and kg

A

1.660539 x 10^-24 g = 1.66054 x 10^-27 Kg

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5
Q

Mass of a proton in amu

A

1.00727647

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6
Q

Mass defect

A

predicted mass of an element (sum of all masses of all protons and neutrons within it) is larger than the actual mass. The mass defect is a result of matter that was converted into energy when nucleus formed.

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7
Q

Nuclear Binding Energy

A

allows protons and neutrons to come together and form nickels. When P and N (nucleons) come together to form nucleus, they are attracted to each other by the STRONG NUCLEAR FORCE, that compensates repulsive force between protons. Energy is released when nucleus is formed and also energy needed to break nucleus. Nucleus is stabled because energy given off when formed

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8
Q

Nuclear binding energy equation

A

E = MC^2 where E is energy in J that is released when nucleus is formed. Mass in Kg. C is speed of light (m/s^2) = 3x10^8

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9
Q

alpha decay

A

alpha particle ejected from unstable nucleus.. Alpha particle has the same composition as He, having 2 protons and 2 neutrons (charge 2+)
U238_92→He2_4+Th 234_90

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10
Q

Beta decay

A

A neutron and loss and a proton is gained, and an electron is emitted. Beta negative decay is the decay of a neutron into a proton with emission of an electron
Beta positive is positron emission. Decay of a proton into a neutron with emission of positron (e+)
Th23490→e−0-1 + Pa234_91

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11
Q

Gamma decay

A

emission of gamma ray, made up of photons, which coverts a high-energy nucleus into a more stable nucleus. A gamma ray has no charge and no mass (energy)—-nucleus goes from excited state to ground state

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12
Q

Half life

A

(grams of element) x 1/2^# of half lives

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13
Q

Exponential decay

A

rate at which radioactive nuclei decay is proportional to the number of nuclei that remain
eta = etanaught x e^-lambdaxt

where eta = number of undecided nuclei. eta naught = # of undercayed nuclei at t=0. Lambda = known decay constant. t= time

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14
Q

Photoelectric effect

A

when light of a sufficiently high frequency (usually blue of UV light) hits a metal in a vacuum, the metal atoms emit (release) electrons called photoelectrons.
Work function: amount of energy needed to free electron (depends on metal)
W = hF_t where H is plank’s constant and f_t is THRESHOLD ENERGY: the min freq of light that causes ejection of electron (depends on metal)

The max kinetic energy in photoelectric effect
K_max = hf-W in other words Kmax = hf = hft

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15
Q

Plank’s constant

A

6.62607004 × 10-34 m2 kg / s

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16
Q

Angular momentum of electron orbiting nucleus

A

L = nh/2pi where n = principal quantum number, h = Planck’s constant. The only variable is the principle quantum number so angular moment of electron changes only with respect to N

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17
Q

Energy of an electron formula

A

E = -R_H/n^2 where Rh is Rydberg unit of energy = 2.18 x 1^-18 J/electron

  • energy proportional to principal quantum number. If you increase n, lower negative number thus higher energy.
  • energy of an electron increases farther out from nucleus that it is located
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18
Q

Absorption

A

an electron can jump from a lower-energy to a higher-energy orbit by absorbing a photon of light of the same frequency as the energy difference between the orbits (absorbed when n increases).
—as an electron go from a lower energy level to a higher energy level they get AHED (absorb light, higher potential, excited, and distant from nucleus

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19
Q

Emission

A

when electron falls from a higher-energy to a lower energy orbit, it emits a photon of light of the same frequency as the energy difference between the orbits. The energy of an emitted photon corresponds to difference in energy between higher energy initial state and lower energy final state
E = hf = hC/lambda = -Rh [1/n^2 initial = 1/n^2 final]

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20
Q

Rydberg Equation

A

to determine amount of light emitted when electron changes energy levels
1/lambda = R (1/i^2 - 1/j^2) I = lower energy level j = higher energy level Rydbergg constant = 2.18 *10^-18 J/electron

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21
Q

Balmer series

A

n> or equal to 3 to n=2, visible light

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22
Q

lymann seriess

A

UV light. N > or equal to two to n = 1

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23
Q

Paschen Series

A

Infared n > or equal to 4 to n = 3

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24
Q

Heisenberg uncertainty principle

A

position and momentum of a particle cannot be accurately measured at the same time; the more accurately you know the momentum, the less you known the position because they are inversely proportional

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25
Q

Ground state

A

state of lowest energy; all electrons in lowest possible orbitals

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26
Q

Excited state

A

when at least one electron moves to subshell higher than normal

27
Q

Principal quantum # (n)

A

indicates main energy level occupied by the electron i.e., what shell electron is. As n increases, avg distance of electron from nucleus. Except for d and f, shell # matches row on periodic table

28
Q

Angular momentum (l)

A

shape of orbital dependent on n (sub shells). L = 0, s orbital. L=1, p orbital. L = 2, d orbital. L= 3, F orbital, L = 4, G orbital

29
Q

Magnetic quantum # (Ml)

A

indicates orientation of orbital around nucleus Ml dependent on L. Ml = -l to +l. S has 1, P has three, and d has five orientations.

30
Q

Spin quantum # (Ms)

A

Ms = + 1/2 up and -1/2 down
When ever two electrons are in same orbital (paired), they have opposite spins. Electrons in different orbitals with same Ms have parallel spins

31
Q

n^2

A

number of orbitals

32
Q

2n^2

A

number of electron in shell

33
Q

Aufbau (building up) principle

A

each subshell will completely fill before electrons began to enter next one

34
Q

Pauli exclusion principle

A

no two electrons in an atom can have the same four quantum #s

35
Q

n+ l rule

A

can be used to rank sub shells by increase energy. Lower sum of n+, the lower energy of the subshell.
e.g., 5d, n-5 and l=2, n+1 = 7
6s, n = 6, l = 0, n+1 = 6
so 5d higher energy than 6s

36
Q

Paramagnetism vs diamagnetism

A

An atom is paramagnetic is it has one or more unpaired electrons pulled into external magnetic field
An atom is diamagnetic, all electrons are paired and they are repelled by external magnetic field
**follow hands rule to build the atom’s electron configuration. If 1 or more orbitals have one electron, atom paramagnetic. If no unpaired electrons diamagnetic.

37
Q

Molecular weight

A

sum of atomic weights of all atoms in a molecule

38
Q

Atomic weight

A

weighted average of the atomic masses of the different isotopes of an element

39
Q

molecular formula

A

exact # of atoms of each element in the compound and is a multiple of the empirical formula

40
Q

empirical formula

A

ratio of elements in compound

41
Q

percent composition (by mass)

A

% of a specific compound that is made up of a given element

—% comp = mass of element in formula/molar mass (g/mol)

42
Q

moles

A

quantity of any substance equal to the number of particles that are found in 12g of C-12. Moles = mass (g)/molar mass (g/mol)

43
Q

Avogadros #

A

6.022x10^23 1/mol

44
Q

1 mole of an ideal gas at STP in liters

A

22.4 L

45
Q

1 mole of any substance = x number of particles

A

6.022x10^23 and also its molar mass in grams (from periodic table)

46
Q

Combination reaction

A

2 or more reactants forming one product

47
Q

Decomposition reaction

A

single reactant broke down into two or more products

48
Q

Combustion reaction

A

involves a fuel, usually a hydrocarbon and O2 (g). Commonly forms CO2 and H20

49
Q

Single displacement reaction

A

an atom/ion in a compound replaced by another atom/ion

50
Q

Double-displacement (Salt metathesis) reaction

A

element from two compounds swap places

51
Q

Neutralization reaction

A

a type of double-replacement reaction where an acid and base react forming a salt and water

52
Q

Limiting reagent (reactant)

A

limits amount of product that can be formed in reaction because it is used up/consumer first.
–All comparisons of reactants must be done in moles

53
Q

Percent yield

A

actual/theoretical x 100

54
Q

Cations

A

positive charged, usually metals

55
Q

anions

A

negative charged, usually nonmetals

56
Q

Oxidation

A

loss of electrons

57
Q

reduction

A

gain of electrons

58
Q

oxidizing agent

A

facilitates oxidation of another compound. Itself is reduced

59
Q

Reducing agent

A

facilitates reduction of another compound. Itself oxidized

60
Q 
Oxidation rules
diatomic or free element
monatomic
1A metals
2A metals
7A metals
H
O
A

o
charge of ion
+1
+2
-1 unless combined with element of greater electronegativity
+1 unless paired with < electronegative atom, then -1
-2 except in peroxides when it is -1 or in compounds with more electronegative elements

61
Q

Balancing redox reaction in acid

A

balance H + O using water and H+

62
Q

Balancing redox reaction in base

A

balance H + O using water + OH=

63
Q

Disproportionation reactions (dismutation)

A

a type of redox reaction in which one element is both oxidized and reduced, forming at least 2 old contains the element with different oxidation states. E.g., decomposition of hydrogen peroxide)
2H2O2 -> 2H20 +O2
oxygen both is reduced and oxidized

MCAT (6 decks)

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