CHEM 101 Unit 1 - Atomic Structure (Questions)

In order, what were the main contributions that shaped atomic theory?

Billiard ball model (Dalton), plum pudding model (Thomson), nuclear model (Rutherford)

What were the hypotheses of the billiard ball model?

1. Matter is composed of extremely small, indivisible particles called atoms

2. An element consists of only one type of atom

3. Atoms of one element differ in properties from atoms of all other elements

4. A compound consists of atoms of two or more elements combined in a small, whole-number ratio

5. Atoms are neither created nor destroyed during a chemical change

Which modern chemical laws were accounted for by the Billiard Ball Model?

1. The Law of Conservation of Matter (atoms are not created or destroyed)

2. Law of Constant Composition (compounds contain set whole number ratios of different elements)

3. Law of Multiple Proportions

How did atomic theory evolve upon the Billiard Ball Model?

The existence of subatomic particles were found through JJ Thomson’s cathode ray experiment (charge to mass ratio) and Milikan’s oil droplet experiment (charge on the electron)

What were the observations from Thomson’s cathode ray experiment? Why was this significant?

Particles were negatively charged, less massive than atoms, and identical for any cathode (any type of metal) → there exists a charged particle smaller than the atom that is universal for all elements

Describe Milikan’s oil droplet experiment. What was its significance?

In a chamber, Milikan produced charged oil droplets that attracted electrons and became negatively charged. Every oil droplet had a charge that was a whole number multiple of the coulomb charge (1.6×10^-19), which cemented this number as the charge on the electron

Describe Rutherford’s gold foil experiment. What was the significance of its observations?

Gold foil was bombarded by alpha particles, and most went straight through the atom, while very rare large deflections were seen. Mostly going through → most of the atom is empty space, large deflection angles → hitting a positively charged mass in the atom. This was the first discovery of the nucleus

What does the atomic mass of the periodic table represent?

Average of all isotope abundances of an element

What are the naming rules of ionic compounds?

1. Name the cation first

2. Add -ide to the name of the anion, leave polyatomic anion as is

3. For metals that form more than one cation, specify the charge in roman numerals

What are the naming rules of binary compounds?

1. Add -ide to the name of the second element

2. Add numerical prefixes (mono, di, tri, etc.) where necessary, but mono is not needed in front of the first element

What are the naming rules of binary acids?

• Named as hydro__ic acid, where the toot of the element used is sandwiched between hydro and ic (my ride has hydraulics)

What are the rules of naming

1. -ite endings: change “ite” to “ous”, add acid at the end of the name

   • Sprite is delicious

2. -ate endings: change “ate” to “ic”, add acid at the end of the name

   • I ate something icky

Which elements form family of 4 oxoanions?

Chlorine, bromine, iodine

Which elements form family of 2 oxoanions?

Nitrogen, sulfur, phosphorus

How do energy and matter differ?

Matter is particulate, with a mass and well-defined position, while energy is wave-like, with no mass or fixed position

What parameters are waves defined by?

Wavelength, frequency, speed

What was the significance of the discovery of the photoelectric effect?

Lead to the hypothesis that EMR is quantized and made up of photons

What were the observations of the photoelectric effect?

1. There is presence of a threshold frequency for each different metal (no electrons leave the surface of the metal below the threshold frequency, regardless of how intense the light is)

2. The intensity of the light shone on the metal affects the intensity of the current (amount of electrons produced)

3. The kinetic energy of the ejected electrons increases as frequency of the incident light increases

In the context of the photoelectric effect, how are intensity (photon number), photocurrent, kinetic energy of electrons, and frequency of the light related?

Intensity and photocurrent are directly correlated, kinetic energy of electrons and frequency of light are directly related

What are the relative distances when plotting energy levels of a Bohr Model electron?

Ground state and first excited state have a big gap, followed by a smaller and smaller gap between each consecutive excited state until the atom is ionized

Do electrons remain in excited states? Why or why not?

The electron always wants to return to its most stable state (ground state), so it will eventually emit a quantum of radiation that will return it to its ground state

To emit the longest wavelength photon, what should the energy transition be?

Shortest energy transition: down only one energy level

To emit the shortest wavelength photon, what should the energy transition be

Longest energy transition: ionization energy to ground state (infinity to 1)

How can you tell radioactivity on the periodic table?

If the mass number is in brackets, the element is radioactive

What quantum numbers are orbitals characterized by?

Principle quantum number (n), angular momentum (l), magnetic quantum number (m_l), electron spin quantum number (m_s)

How do you determine angular momentum number (l) of an orbital?

0 - (n-1)

How do you determine magnetic quantum number (m_l) of an orbital?

-l to l from right to left, increases by 2 for every new orbital type

How do you determine electron spin quantum number (m_s) of an orbital?

+1/2 for upwards spin, -1/2 for downwards spin