Atomic and Nuclear Structure

Question 1

A = Atomic …

Answer 1

Atomic Mass Number

Total number of protons + neutrons.

Question 2

Z = Atomic …

Answer 2

Atomic Number. Total number of protons.

Determines the number of electrons, and therefore the chemical properties of the atom.

Question 3

A - Z = …

Answer 3

A - Z = atomic mass number - number of protons = number of neutrons.

Question 4

Isotopes have …

Answer 4

Same number of protons, different number of neutrons.

Same chemical behavior, different mass, and different nuclear decay properties.

Question 5

Energy-mass relation?

Energy–momentum relation?

Answer 5

E = mc^2

E^2 = (pc)^2 + (m_0c^2)^2

Question 6

Electron mass?

How many times the proton mass?

Answer 6

0.511 MeV

roughly 1/1800 of proton or neutron mass

Question 7

Proton mass?

More or less than neutron mass?

How many times the electron mass?

Answer 7

938.3 MeV

A bit less than neutron mass.
roughly 1836 times electron mass

Question 8

Neutron mass?

More or less than proton mass?

Answer 8

939.6 MeV

A bit more than proton mass

Question 9

Electron Orbits - Principle quantum

Letters, and number of electrons.

Answer 9

Letters: K, L, M, N, O, …
Principle Quantum number: 1, 2, 3, 4, 5, …

Number of electrons 2n^2
n = quantum number

Question 10

Electron binding energy vs. proximity to nucleus?

Answer 10

Electron binding energy increases with proximity to the nucleus by radius squared (r^2).

Closer to nucleus means lower energy level (more favorable).

Question 11

Change in electron orbit results in / is caused by?

Answer 11

Release and absorption of energy.

Absorbed energy pushes electron in higher orbit (excitation) or frees it from atom if the absorbed energy is larger than its binding energy (ionization).

Falling down from higher to lower orbits releases energy equal to the energy difference of the two shells.
Energy is either transferred to higher shell electrons, which will be ejected from the atom as an Auger electron.
or
emitted in the form of a characteristic x-ray (photon)

Question 12

What defines the chemical properties of an atom?

Answer 12

Number of protons (Z).

Same number of protons but different number of neutrons are the isotopes of an atom.

Question 13

The four fundamental forces in nature?

Answer 13

Strong Nuclear Force - “glues” the nucleus together - 1

Electromagnetic (Coulombic) Force - attraction and repulsion of charged particles - 1/37

Weak Nuclear Force - inside particles - 10^-6

Gravity - 10^-39

Question 14

Which fundamental forces are infinite, which are short ranged?

Answer 14

Infinite: Gravity and EM (1/r^2 dependence)

Short ranged (few femtometers): Strong and weak forces.

Question 15

Size of hydrogen nucleus and electron cloud.

Answer 15

Nucleus: 1.70 fm (Femtometer = 1 × 10^-15 m)

Electron cloud: ~ 0.1 nm = 1 × 10^-10 m = 1 Å

Question 16

Excitation of an atom means …

Answer 16

A electron is moved from a given shell to a higher n shell that is either empty or does not contain a full complement of electrons.

Question 17

Ionization of an atom means …

Answer 17

A electron is removed from the atom (i.e. the electron is supplied with enough energy to overcome its binding energy in a shell).

Question 18

Auger electron

Answer 18

Electron which is ejected from atom because it received energy from an other electron falling into a lower orbit.