Ch 1 - Atomic Structure

Question 1

What is the charge and mass of a proton?

Answer 1

\+1
1 amu (atomic unit charge)

Question 2

What is the atomic number?

Answer 2

Z

- equal to the number of protons found in an atom of that element

Question 3

What is the charge and mass of a neutron?

Answer 3

• charge of 0

- about 1 amu; mass is slightly larger than a proton and together they make up almost the entire mass of an atom

Question 4

What is a mass number (atomic mass)?

Answer 4

A

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

Question 5

What are isotopes?

Answer 5

atoms that share an atomic number but have different mass numbers (different number of neutrons)

Question 6

What are electrons? What is their charge?

Answer 6

• move through the space surrounding the nucleus and are associated with varying levels of energy
• charge of -1

Question 7

How do the electrostatic and gravitational forces of attraction react in relation to protons and electrons?

Answer 7

because subatomic particles’ masses are so small, the electrostatic force of attraction between the unlike charges of the proton and electron is far greater than the gravitational fore of attraction based on their respective masses

Question 8

What are electron shells and what determines their energy levels?

Answer 8

• electrons move around the nucleus at varying distances, which correspond to varying levels of electrical potential energy
• electrons closer to the nucleus are at lower energy levels and electrons in higher electron shells have higher energy levels

Question 9

What are valence electrons?

Answer 9

• electrons that are farthest away from the nucleus with the strongest interactions with the surrounding environment and the weakest interaction with the nucleus
• more likely to become involved in bonds with other atoms because they experience the least electrostatic pull from their own nucleus

Question 10

What is the difference between a cation and anion?

Answer 10

• cation: positively charged atom, loss of electron

- anion: negatively charged atom, gain of electron

Question 11

When do the number of protons equal the number of electrons?

Answer 11

in a neutral atom

Question 12

What is the atomic weight?

Answer 12

• the weighted average of the different isotopes of an element
• the number reported on the periodic table

Question 13

What is Avagadro’s number?

Answer 13

NA = 6.02 x 10^23/mol

Question 14

What is quantum?

Answer 14

energy difference between energy levels first described by Planck

Question 15

How is the energy of quantum determined?

Answer 15

E=hf (Energy = Plank’s constant x frequency)

Question 16

What is quantization?

Answer 16

• there is not an infinite range of energy levels available to an electron; electrons can exist only at certain energy levels
• the energy of an electron increases the farther it is from the nucleus

Question 17

What is angular momentum of an electron?

Answer 17

Bohr’s model
L = (nh)/(2pi)
the angular momentum changes only in discrete amounts with respect to the principal quantum number

Question 18

How did Bohr calculate the energy of an electron?

Answer 18

E = -Rh/n^2
Rh (Rydberg unit of energy) = 2.18 x 10^-18 J/electron
- energy of an electron changes in discrete amounts with respect to the quantum number
- the energy of an electron increases the farther out from the nucleus that it is located (increasing n)

Question 19

What is the difference between a ground state and an excited state?

Answer 19

• ground: state of lowest energy where all electrons are in the lowest possible orbitals
• excited: when at least one electron has moved to a subshell of higher than normal energy

Question 20

What happens to electrons as they go from a lower energy level to a higher energy level?

Answer 20

AHED

• Absorb light
• Higher potential
• Excited
• Distant (from nucleus)

Question 21

How can electrons be excited and how long do they stay excited?

Answer 21

• by heat or other energy forms
• brief lifetime causing electrons to go back to ground state causing emission of energy in the form of photons with a specific wavelength

Question 22

How can the electromagnetic energy of a photon be determine?

Answer 22

E = hc/lambda

Question 23

What is the line spectra?

Answer 23

• spectrum of light at specific frequencies where each line on the emission spectrum corresponds to a specific electron transition

Question 24

What is an atomic emission spectrum?

Answer 24

• different to each element since each require different amount of energy to return to ground state from excited (photon emitted)
• can be used as a fingerprint for the element

Question 25

What is the difference between the Lyman, Balmer, and Paschen series?

Answer 25

- lyman: the group of hydrogen emission lines corresponding to transitions from energy levels n>=2 to n=1 (larger energy transitions, shorter photo wavelengths) - balmer: energy levels n>=3 to n=2 - paschen: n>=4 to n =3

Question 26

What is the equation for energy when Bohr and Plank are combined?

Answer 26

E = -R(1/ni^2 - 1/nf^2) the energy of the emitted photon corresponds to the difference in energy between the higher-energy initial state and lower energy final state - +E emission, -E absorption

Question 27

What is absorption spectra?

Answer 27

exciting the electrons of a particular element to jump from lower energy level to higher results in energy absorption at specific wavelengths (photon absorbed)

Question 28

What is Heisenberg uncertainty principle?

Answer 28

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

Question 29

What is Pauli exclusion principle?

Answer 29

no 2 electrons in a given atom can posses the same set of 4 quantum numbers

Question 30

What is the principal quantum number?

Answer 30

- n - any positive integer value - the larger n, the higher the energy level and radius of the electron's shell

Question 31

What is the maximum number of electrons within a shell? What is the relationship between shell distance and energy?

Answer 31

2n^2 | - the difference in energy between 2 shells decreases as the distance from the nucleus increases

Question 32

What is the angular momentum number?

Answer 32

- l = 0 --> n-1 | - refers to the shape and number of subshells within a given principal energy level

Question 33

What is the spectroscopic notation?

Answer 33

s --> l=0 (2 electrons) p --> l=1 (6 electrons) d --> l=2 (10 electrons) f --> l=3 (14 electrons)

Question 34

What is the maximum number of electrons within a subshell?

Answer 34

4l+2

Question 35

What is the magnetic quantum number?

Answer 35

- ml = -l --> +l - specifies the particular orbital within a subshell where an electron is most likely to be found at a given moment in time

Question 36

What is the spin quantum number?

Answer 36

- ms = +/- 1/2 - whenever 2 electrons are in the same orbital, they must have opposite spins (paired) - electrons in different orbital with the same ms value (parallel spins)

Question 37

What is the electron configuration?

Answer 37

- for a given atom or ion, the pattern by which subshells are filled, as well as the number of electrons within each principal energy level and subshell using spectroscopic notation

Question 38

What is Aufbau principle?

Answer 38

- electrons fill from lower to higher energy subshells | - each subshell will fill completely before electrons begin to enter the next

Question 39

What is Hund's rule?

Answer 39

within a given subshell, orbitals are filled such that there are a maximum number of half-filled orbitals with parallel spins (crowded bus)

Question 40

What are the 2 exceptions to Hund's rule?

Answer 40

half filled and fully filled orbitals have lower energies (higher stability) than other states - Cr (z=24) [Ar] 4s13d5 making d shell half filled and more stable - Cu 9z=29) [Ar]4s13d10 making d shell full and more stable

Question 41

What is the difference between paramagnetic and diamagnetic?

Answer 41

- para: materials composed of atoms with unpaired electrons will orient their spins in alignment with a magnetic field, and the material will thus be weakly attracted to the magnetic field - di: materials consisting of atoms that have only paired electrons will be slightly repelled by a magnetic field

Question 42

What are the 3 isotopes of hydrogen?

Answer 42

- protium - deutrium - tritium

Question 43

What did Rutherford do?

Answer 43

first postulated that the atom had a dense, positively charged nucleus that made up only a small fraction of the volume of the atom

Question 44

What is Bohr's model?

Answer 44

a dense, positively charged nucleus is surrounded by electrons revolving around the nucleus in orbits with distinct energy levels

Question 45

Which orbital are valence electrons found for each group?

Answer 45

- for representative groups (group 1-2 and 13-18), s and/or p orbitals - for transition groups, s and either d or f orbitals

Question 46

Where are electrons removed from when forming a cation?

Answer 46

from the subshell with the highest n value (s)