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MCAT-GENERAL CHEMISTRY > Atomic Structure and Periodic Trends > Flashcards

Atomic Structure and Periodic Trends Flashcards

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1
Q

what is the smallest unit of any element?

A

an atom

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2
Q

all atoms have a central nucleus that contains:

A

protons and neutrons

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3
Q

what are nucleons?

A

protons and neutrons

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4
Q

what is contained outside the nucleus in an atom?

A

electrons that are held by the electrostatic attraction of the positively charged nucleus

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5
Q

atomic number Z

A

the number of protons in the nucleus of an atom (subscript)

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6
Q

mass number A

A

the number of protons plus the number of neutrons in the nucleus of an atom (superscript)

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7
Q

what is another way to write the mass number?

A

as a number after the name of the element

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8
Q

isotopes

A

two atoms of the same element that have the same atomic number but different mass numbers due to their difference in the number of neutrons

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9
Q

atomic weight of an element

A

the weighted average of the masses of its naturally occurring isotopes

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10
Q

anion

A

a negatively charged ion

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11
Q

cation

A

a positively charged ion

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12
Q

strong nuclear force

A

the force that holds protons and neutrons together, the strongest force (stronger than the electrical force between charged particles)

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13
Q

radioactive

A

unstable nuclei

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14
Q

radioactive decay

A

a process radioactive nuclei undergo to make them more stable; by altering the number and ratio of protons and neutrons or just lowing their energy

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15
Q

what are the three types of radioactive decay?

A

alpha, beta (-, +, electron capture), gamma

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16
Q

parent

A

the nucleus that undergoes radioactive decay

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17
Q

daughter

A

the resulting more stable nucleus after radioactive decay

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18
Q

alpha decay

A

becomes more stable by reducing the number and neutrons by emitting an alpha particle (containing 2 neutrons and protons)

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19
Q

each type of beta decay involves:

A

the conversion of a neutron into a proton or vice versa through the action of the weak nuclear force

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20
Q

why are beta particles more dangerous than alpha particles?

A

they are significantly less massive so have more energy and greater penetrating ability

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21
Q

beta- decay

A

occurs when an unstable nucleus contains too many neutrons: converts a neutron into a proton and an electron (beta - particle), the beta- particle is ejected

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22
Q

what is the effect on atomic number and mass number of beta-decay?

A

atomic number is 1 greater, mass number is the same

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23
Q

which is the most common type of beta decay?

A

beta- decay

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24
Q

beta+ decay

A

occurs when an unstable nucleus contains too few neutrons: converts a proton into a neutron and a positron which is ejected

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25
Q

what is the effect on atomic number and mass number of beta+decay?

A

atomic number is one less, the mass number remains the same

26
Q

electron capture

A

allows the unstable nucleus to increase its number of neutrons by capturing an electron from the closest electron shell to convert a proton into a neutron

27
Q

what is the effect on atomic number and mass number of electron capture?

A

the atomic number is one less, the mass number remains the same

28
Q

gamma decay

A

a nucleus in an excited energy state (after alpha or beta decay) relaxes back to ground state by emitting energy in the form of photons of electromagnetic radiation (gamma photons)

29
Q

why are gamma photons the most dangerous?

A

they have neither mass or charge and a very high frequency/energy, therefore they penetrate matter most effectively

30
Q

what is the effect on atomic number and mass number of gamma decay?

A

no change in atomic number of mass number

31
Q

half-life

A

the time it takes for one half of some sample of the substance to decay

32
Q

how does the amount of a radioactive substance change over time?

A

it decreases exponentially

33
Q

nuclear binding energy

A

the energy released when individual nucleons (protons and neutrons) were bound together to form the nucleus, also equal to the energy that would be required to break up the intact nucleus into individual nucleons

34
Q

the greater the binding energy per nucleon…

A

the more stable the nucleus

35
Q

mass defect

A

the difference in mass resulting from conversion of some mass to energy when the nucleons bind to form a nucleus

36
Q

the mass defect’s energy equivalent is:

A

the nuclear binding energy

37
Q

what sort of mass defect should a stable nucleus have?

A

positive

38
Q

Planck’s constant

A

h=6.63*10^-34 Js

39
Q

describe the Bohr model

A

electrons orbit the nucleus in circular paths, distance from nucleus was related to energy of the electrons, only orbits at certain distances were allowed; corresponding with quantized energy states to support the specific wavelengths observed in emission line spectra. ONE ELECTRON ONE ATOM MODEL

40
Q

ground state

A

lowest possible energy level of an electron, n=1

41
Q

excited state

A

when an electron absorbs a photon corresponding to energy difference between levels, allowing it to jump to a higher energy level

42
Q

what does the Bohr model not account for?

A

electron-electron interactions in many-electron atoms

43
Q

orbital

A

a three-dimensional region around the nucleus in which the electron is most likely to be found

44
Q

what are the three basic rules for electron configuration?

A

1) electrons occupy the lowest energy orbitals available (Aufbau principle)
2) electrons in the same subshell occupy available orbitals singly before pairing up (Hund’s rule)
3) there can be no more than two electrons in a given orbital (Pauli exclusion principle)

45
Q

diamagnetic

A

an atom that has all of its electrons spin-paired, contains an even number of electrons and have all of its occupied subshells filled: NO NET MAGNETIC FIELD

46
Q

how do diamagnetic atoms behave in the presence of an external magnetic field

A

they will be repelled

47
Q

paramagnetic

A

electrons are not all spin-paired

48
Q

how do paramagnetic atoms behave in the presence of an external magnetic field

A

they will be attracted

49
Q

some anomalies in electron configurations have atoms that prefer a filled or half-filled d subshell, some examples include:

A
  • chromium (fill d shell with 5e-, Z=24)
  • copper (fill d subshell with a 4s e-, Z=29)
  • molybdenum (Z=42)
  • silver (Z=47)
  • gold (Z=79)
50
Q

where do atoms go in anions?

A

the first available orbital, the one with the lowest available energy

51
Q

isoelectronic

A

atoms with the same electron configuration

52
Q

which atoms are removed/ionized from an atom first?

A

always comes from the valence shell (highest n shell) and the highest energy orbital within that level)

53
Q

which electrons are responsible for the chemical reactivity of each group in the periodic table?

A

the valence-shell electron configuration

54
Q

nuclear shielding effect

A

each filled shell between the nucleus and the valence electrons shields the valence electrons from the full effect of the positively charged protons in the nucleus

55
Q

effective nuclear charge, Zeff

A

the charge felt by valence electrons after nuclear shielding

56
Q

first ionization energy IE1

A

the amount of energy necessary to remove the least tightly bound electron from an isolated atom

57
Q

second ionization energy IE2

A

the amount of energy required to remove the least tightly bound electron from the cation

58
Q

is IE1 or IE2 always greater?

A

IE2 is always greater than IE1

59
Q

electron affinity

A

the energy associated with the addition of an electron to an isolated atom

60
Q

what does it mean if the electron affinity of an atom is negative?

A

energy is released when the electron is added

61
Q

what does it mean if the electron affinity of an atom is positive?

A

energy is required in order to add the electron

62
Q

electronegativity

A

a measure of an atom’s ability to pull electrons to itself when it forms a covalent bond

MCAT-GENERAL CHEMISTRY (6 decks)

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