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MCAT: General Chemistry > Ch. 1: Atomic Structure > Flashcards

Ch. 1: Atomic Structure Flashcards

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1
Q

Where are protons located in an atom and what is their unit of charge?

A

Protons are located in the nucleus and each proton has a charge equal to 1.6x10^-19 C

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2
Q

What is the atomic number (Z) of an element?

A

The number of protons found in an atom of that element. It is the number above the element symbol in the periodic table.

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3
Q

What is the mass of a proton in amu?

A

1 amu

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4
Q

Where are neutrons located in an atom and what is their unit of charge?

A

Neutrons are located in the nucleus and are electrically neutral.

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5
Q

How does the mass of a neutron compare to a proton?

A

A neutron’s mass is slightly larger than that of the proton

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6
Q

What is the mass number (A) of an atom?

A

The sum of the protons and neutrons in the atom’s nucleus

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7
Q

What are isotopes?

A

Atoms that share an atomic number (# protons) but have different mass numbers (# protons + # neutrons)

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8
Q

What is the difference between a protium, deuterium, and tritium of hydrogen?

A

Protium: 1 proton, 0 neutron = mass number is 1
Deuterium: 1 proton, 1 neutrons = mass number is 2
Tritium: 1 proton, 2 neutrons = mass number is 3

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9
Q

Where are electrons located in an atom and what is their charge?

A

Electrons move through the space surrounding the nucleus and are associated with varying levels of energy. Each electron has a negative charge of 1.6x10^-19 C.

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10
Q

How does the mass of an electron compare to a proton?

A

The mass of an electron is approximately 1/2000 of a proton - much smaller!

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11
Q

What is the difference between electrons closer to the nucleus and electrons farther out?

A
  • Electrons closer to the nucleus are at lower energy levels
  • Electrons farther out have higher energy and stronger interactions with the surrounding environment but weaker interactions with the nuclues
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12
Q

What are valence electrons?

A

Electrons farthest from the nucleus that have the strongest interactions with the surrounding environment. This allows them to form bonds with other atoms due to having the least electrostatic pull from their nucleus.

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13
Q

How is the size of the atomic mass unit defined?

A

1 amu is 1/12 the mass of the carbon-12 atom, which is approximately 1.66x10^-24 g. Since the carbon-12 nucleus has 6 protons and 6 neutrons, an amu is approximately equal to the mass of a proton or neutron.

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14
Q

What is atomic weight?

A

The weighted average of naturally occurring isotopes of that element.

Example: the atomic weight of bromine is 79.9 amu because of the average of bromine-79 and bromine-81 which occur in almost equal proportions.

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15
Q

How does atomic weight relate to Avogadro’s number? Carbon example?

A

The atomic weight represents the mass of ONE mole of the element, in grams. A mole is a number of “things” equal to Avogadro’s number (6.02x10^23).

Example: the atomic weight of carbon is 12 amu, which means that the average carbon atom has a mass of 12 amu AND 6.02x10^23 carbon atoms have a combined mass of 12 grams.

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16
Q

Why is atomic mass essentially equal to mass number?

A

The atomic mass IN AMU is essentially equal to mass number because 1 amu is approximately equal to the mass of a proton or neutron.

Mass number is the sum of protons and neutrons in the nucleus.

Atomic mass is the mass of the atom in amu (electrons are negligible).

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17
Q

What is the difference between atomic mass and atomic number?

A

Atomic number (Z) is the number of protons in the nucleus.

Atomic mass is the mass of the atom (protons + neutrons) in amu.

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18
Q

What does Planck’s equation (E=hf) tell us?

A

The energy emitted as electromagnetic radiation from matter comes in discrete bundles called quanta.

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19
Q

What does the Bohr model of angular momentum and electron energy tell us? Write down equations!

A

-Bohr placed restrictions for the angular momentum of an electron orbiting a nucleus by L= (nh/2pi), where n is the principal quantum number

-Bohr stated that the energy of an electron changes in discrete amounts with respect to the quantum number. The energy of an electron INCREASES the farther from the nucleus it is located (INCREASING n).
E= -(RH/n^2)

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20
Q

What equation is used to determine the electromagnetic energy of photons emitted when electron returns to its ground state?

A 
E = hf and f = (v/λ)
E = h(v/λ)
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21
Q

What are atomic emission spectrum?

A

Each element has a unique atomic emission spectrum because each element can have its electrons excited to a different set of distinct energy levels.

Photons of energy are emitted when an electron goes from a higher energy state to a lower energy state.

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22
Q

What equation is used to calculate the energy of the emitted photon from one energy state to another?

A

E = h(v/λ) = - RH (1/ni^2 - 1/nf^2)

23
Q

What are atomic absorption spectrum?

A

Photons of energy are absorbed when an electron goes from a lower energy state to a higher energy state.

24
Q

What happens as electrons go from a lower energy level to a higher energy level (AHED)?

A

Absorb light
Higher potential
Excited
Distant (from the nucleus)

25
Q

What is the Heisenberg uncertainty principle?

A

It is impossible to simultaneously determine, with perfect accuracy, the momentum and the position of an electron.

26
Q

What is the Pauli exclusion principle?

A

No two electrons in a given atom can possess the same set of four quantum numbers.

27
Q

What does the principal quantum number represent?

A

SIZE: The larger the integer value of n, the larger the radius and energy level of the electron’s shell.

28
Q

What equation is used to calculate the maximum number of electrons within a shell?

A

2n^2

29
Q

Fill in the blank: The difference in energy between two shells ______ as the distance from the nucleus _____. Why?

A

The difference in energy between two shells INCREASES as the distance from the nucleus INCREASES because the energy difference is a function of (1/ni^2 - 1/nf^2)

30
Q

What does the second (azimuthal) quantum number represent?

A

It represents SHAPE and the # OF SUBSHELLS within a given principal energy level (shell)

31
Q

How does n restrict l?

A

For any given value of n, the range of possible values for l is 0 to (n-1).

32
Q

What are letters denoting subshells of l = 0, l = 1, l =2, and l =3 ?

A 
l = 0  ----- s
l = 1 ----- p
l = 2 ----- d
l = 3 ----- f
33
Q

What does the magnetic quantum number represent?

A

It specifies the particular ORBITAL within a subshell where an electron is most likely to be found at a given moment in time.

34
Q

How many electrons can an orbital hold?

A

Max of 2

35
Q

How does the second quantum number restrict the magnetic quantum number?

A

The possible values of ml are the integers between -l to +l including 0.

36
Q

How are l and ml connected mathematically?

A

For any value of l, there will be 2l+1 possible values of ml.

37
Q

What is the spin quantum number?

A

There are two spin orientations designated for electrons: -1/2 and +1/2

38
Q

What is the difference between paired and unpaired spins?

A

Paired: two electrons are in the same orbital must have opposite spins

Parallel: Electrons in different orbitals with the same spin

39
Q

What is the Aufbau (building up) principle?

A

Each subshell will fill completely before electrons begin to enter the next one

40
Q

What rule is used to determine which subshell will fill first?

A

n + l rule: The lower the sum of the values of the first and second quantum numbers, the lower the energy of the subshell.

If they possess the same n+l value, the subshell with the lower n has lower energy and will fill first.

Remember: 0 - s, 1 - p, 2 - d, 3 - f

41
Q

How do you determine the electron configuration of anions?

A

Additional electrons fill the next subshells like normal.

42
Q

How do you determine the electron configuration of cations?

A
  1. Write out the electron configuration of the neutral atom
  2. Remove electrons from the subshells with the highest value of n first
  3. If multiple subshells are tied for the highest n, then electrons are removed from the subshell with the highest l value
43
Q

What is the electron configuration of Fe+3?

A

Neutral: [Ar] 4s2 4d6
Cation: [Ar] 3d5

44
Q

What is Hund’s rule?

A

Within a given subshell, orbitals are filled such that there are a maximum number of half filled orbitals with parallel spins. The basis of this preference is electron repulsion.

45
Q

What is the electron configuration of copper and chromium?

A

Copper: [Ar] 4s1 3d10
Chromium: [Ar] 4s1 3d5

Half filled and fully filled orbitals have lower energies (higher stability) than other states.

46
Q

What is paramagnetism and how does it real to the spins of electrons?

A

Atoms with UNPAIRED electrons will orient theirs in alignment with the magnetic field making them weakly attracted to it.

PARAmagnetic: magnetic field will cause PARAllel spins in unpaired electrons.

47
Q

What is diamagnetism and how does it relate to the spins of electrons?

A

Atoms that have ONLY PARIED electrons will be slightly repelled by a magnetic field, which can cause levitation.

48
Q

What are valence electrons?

A

Electrons that are in atom’s outermost energy shell, are most easily removed, and are available for bonding.

49
Q

Where are the valence electrons of groups 1-2?

A

highest s subshell

50
Q

Where are the valence electrons of groups 13-18?

A

highest s and p subshells

51
Q

Where are the valence electrons of the transition metals?

A

highest s and d subshells

52
Q

Where are the valence electrons of the lanthanide series?

A

highest s and f subshells

53
Q

What equation is used to calculate the total number of electrons that can fill a subshell? shell?

A

subshell: 4l+2
shell: 2n^2

MCAT: General Chemistry (11 decks)

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