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MCAT > General Chemistry Review > Flashcards

General Chemistry Review Flashcards

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MCAT flashcards
1
Q

What is the fundamental unit of charge that each proton has an amount of charge equal to?

A

e = 1.6 x 10^-19 C

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2
Q

For the proton, how is the fundamental unit of charge denoted?

A

+1e or simply +1

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3
Q

What is the mass of a proton?

A

Approximately one atomic mass unit (amu)

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4
Q

What is the atomic number (Z) equal to?

A

The number of protons found in an atom of an element

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5
Q

Why is the atomic number (Z) useful?

A

It uniquely identifies an element because elements are defined by the number of protons they contain

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6
Q

Compared to a proton, how does a neutron’s mass differ?

A

The neutron’s mass is only slightly larger than a proton’s

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7
Q

Which subatomic particles comprise almost the entire mass of an atom?

A

Protons and neutrons

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8
Q

What is the characteristic mass number (A)?

A

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

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9
Q

What is an isotope?

A

Atoms that share an atomic number but have different mass numbers

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10
Q

What are the three naturally occurring carbon isotopes?

A

12C, 13C, 14C

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11
Q

What value is an electron’s charge equal to?

A

-1e or simply -1

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12
Q

Where do electrons move around?

A

In the space surrounding the nucleus

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13
Q

Why is the electrostatic force of attraction between the unlike charges of a proton and electron far greater than the gravitational force of attraction based on their masses?

A

Because a proton and electron’s mass is so small, it’s almost insignificant. Therefore, the predominating force of attraction is related to their opposite charges

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14
Q

How do we know electrons have varying levels of electrical potential energy?

A

Because electrons move around the nucleus at varying distances which correspond to varying levels of electrical potential energy

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15
Q

Which electrons are at lower energy levels? Higher energy levels?

A

Electrons closer to the nucleus are at lower energy levels and electrons farther out are at higher energy levels

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16
Q

Why do electrons who are farther out from the nucleus have higher energy?

A

Because they are in higher electron shells. Also, they have the strongest interactions with the surrounding environment and the weakest interactions with the nucleus

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17
Q

Why are valence electrons farther from the nucleus?

A

Because they are more likely to become involved in bonds with other atoms since they experience the least electrostatic pull from their own nucleus

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18
Q

What do valence electrons determine?

A

The reactivity of an atom

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19
Q

What does the sharing or transferring of valence electrons in bonds accomplish for elements?

A

Allows elements to fill their highest energy level to increase stability

20
Q

Which subatomic particle is the most important for determining 1) charge, 2) atomic number, and 3) isotope?

A

1) Charge - electron
2) Atomic number - proton
3) Isotope - neutron

20
Q

What is the difference between atomic mass/mass number and atomic weight?

A

Atomic weight is constant for a given element and is reported in the periodic table.

Atomic mass/mass number varies from one isotope to another.

20
Q

Mass number (A) =

A

Number of protons + Number of neutrons

21
Q

In nuclear medicine, isotopes are created and used for various purposes; for instance, 18^O is created from 18^F. Determine the number of protons, neutrons, and electrons in each of these species.

A

18^O: 8 protons, 10 neutrons, 8 electrons
18^F: 9 protons, 9 neutrons, 9 electrons

22
Q

In a neutral atom, number of protons =

A

Number of electrons

23
Q

What is the size of the atomic mass unit defined exactly as?

A

1/12 of the mass of a carbon 12 atom, approximately 1.66 x 10^-24 g

24
Q

Explain one amu being equal to 1/12 of a carbon 12 atom?

A

A carbon 12 atom has 6 protons and 6 neutrons. Because protons and neutrons have a negligible difference in mass, one proton or one neutron is equal to the mass of one atom.

25
Q

How are isotopes named/referred to?

A

The name of the element followed by the mass number

26
Q

Which element has three isotopes that are the only ones given specific names? What are the names?

A

Hydrogen:
Protium (one proton, atomic mass of 1 amu)
Deuterium (one proton and one neutron, atomic mass of 2 amu)
Tritium (one proton and two neutrons, atomic mass of 3 amu)

26
Q

Why do isotopes generally exhibit the same properties?

A

Because they have the same number of protons and electrons

27
Q

What is atomic weight?

A

The weighted average of different naturally occurring isotopes; it is also the number reported on the periodic table.

Different isotopes are usually present in the same proportions in any sample of naturally occurring element.

28
Q

What is the significance of half-life?

A

Half-life corresponds with stability and it also helps determine the relative proportions of these different isotopes.

Longer-lasting isotopes are generally more abundant.

29
Q

What is a mole?

A

A number of “things” equal to Avogadro’s number:
Na=6.02 x 10^23

30
Q

Mnemonic for atomic mass vs atomic weight.

A

Atomic mass is the mass number.

Atomic weight is the weighted average of naturally occurring isotopes of that element.

31
Q

What is quanta?

A

Discrete bundles of energy emitted as electromagnetic radiation from matter

32
Q

What is the Planck relation and what does it tell us?

A

Planck relation: E=hf
(h is Planck’s constant = 6.626 x 10^-34 Js, f =frequency of radiation)

Gives the energy of a quantum.

33
Q

What did Neils Bohr postulate?

A

The centripetal force acting on the electron as it revolved around the nucleus was created by the electrostatic force between the positively charged proton and the negatively charged electron

34
Q

What is the equation for angular momentum and what does it tell us?

A

L = (nh)/(2pi)
(n= principal quantum number which can only be positive, h =planck’s constant)

35
Q

How do we know that the angular momentum of an electron changes only in discrete amounts with respect to the principal quantum number)?

A

The Planck relation (L=nh/2pi) shows principal quantum number as the only variable

36
Q

What is the energy equation and what does it tell us?

A

E = -Rh/n^2
(Rh=Rydberg unit of energy=2.18x10^-18 J/electron)

Tells us that the energy of the electron changes in discrete amounts with respect to quantum number.

The energy of an electron increases (becomes less negative) the farther out from the nucleus that it is located (increasing n).

While the magnitude of the fraction is getting smaller, the actual value it represents is getting larger (less negative)

37
Q

Why is there a negative sign in the Rydberg equation?

A

A value of 0 was assigned to the state in which the proton and electron are separated completely, meaning that there is no attractive force between them.

Therefore, any electron in any of its quantized states will have an attractive force toward the proton, giving the equation a negative sign.

38
Q

How would an electron jump from one orbit to another?

A

If one transfers an amount of energy exactly equal to the difference between one orbit and another, this could result in the electron “jumping” from one orbit to a higher-energy one

39
Q

What is the ground state of an atom?

A

The state of lowest energy in which all electrons are in the lowest possible orbitals

40
Q

When is an atom in an excited state?

A

When at least one electron has moved to a subshell of higher than normal energy

41
Q

What are the applications of the Bohr Model?

A

The Bohr model of the hydrogen atom is useful for explaining the atomic emission and absorption spectra of atoms

42
Q

When do electrons emit amounts of energy?

A

When they return from their excited state

43
Q

What equation determines the electromagnetic energy of emitted photons?

A

E = hc/wavelength
(h=Planck’s constant, c=speed of light=3.00 x 10^8 m/s)

This is a combination of two other equations: E=hf and c=f*wavelength

44
Q
A

MCAT (2 decks)

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