Unit 1 Study

Question 1

For which would de broglie wavelength be significant: an electron or a golf ball?

Answer 1

An electron

Question 2

The lines in an atomic line emission spectrum are due to

Answer 2

the movement of electrons from higher energy states to lower energy states in atoms

Question 3

A line spectrum is to an element as what is to a person?

Answer 3

Fingerprint

Question 4

The Balmer series of lines for for the hydrogen atom are found only in the visible region of the spectrum

Answer 4

False. This is because transitions higher than 7 —> 2 are UV

Question 5

Which of the following statements about the spectral lines of hydrogen is true according to the Bohr model

Answer 5

They have frequencies which depend directly on the differences in energy between energy levels; This is because of E=hv

Question 6

The Bohr theory of the hydrogen atom

Answer 6

accounts for the fact that light of only certain wavelengths is given off when a hydrogen atom is excited

Question 7

An electron in a hydrogen atom could undergo any of the transitions listed bellow, by emitting light. Which transition would give the shortest wavelength?

Answer 7

n=4 to n=1; This is because photons with shorter wavelengths have more energy than those with longer wavelengths. n=1 is the lowest energy level, the energy increases as n increases. A transition from n=4 to n=1 will release more energy that any other option given.

Question 8

Why was classical mechanics able to explain the world just fine up until then?

Answer 8

Macroscopic objects can be modeled purely as particles because their wavelength is so small compared to their scale that it can be neglected for most purposes and still give a goo description of their behavior

Question 9

The mass number of an atom is the umber of protons in the nucleus

Answer 9

plus the number of neutrons; That is because the mass number= number of protons + number of neutrons

Question 10

What is true about sodium atoms (Na) ?

Answer 10

Isotopes of sodium exist, so not all sodium atoms have the same number of neutrons.

Question 11

Descriptions of an atomic number

Answer 11

The atomic number of an elements is equal too the number of protons in that elements nucleus. The number of protons defines an element and cannot be changes without changing the element. protons have a +1 charge. In a neutral atom (total charge of 0), the number of electrons must equal the number of protons because electrons have a -1 charge

Question 12

How do you find relative abundance?

Answer 12

Take the relative abundance of each isotope and multiply them by their corresponding isotopes atomic mass. Add all of the products together to find the average atomic mass

Question 13

A new element has two isotopes, one with a mass of 40.0 amu and the other with a mass of 42.0 amu. The atomic weight is 40.50 g/mol. What is the true statement?

Answer 13

The isotope at 40.0 amu is more abundant; That is because the atomic weight is weighted average of the masses of all possible isotopes. The more abundant isotope will skew the average closer to its mass. 40.50 g/mol is closest to 40.0 amu

Question 14

For which would de Broglie wavelength be significant: an electron or a golf ball?

Answer 14

An electron

Question 15

The electromagnetic spectrum

Answer 15

is divided into seven named regions, each containing a range of wavelengths (or frequencies)

Question 16

Low frequency, long wavelength

Answer 16

Radio waves, infrared radiation, visible light, ultraviolet radiation

Question 17

Why are x-rays dangerous

Answer 17

They are dangerous because they have high energy photons capable of ionizing molecules.

Question 18

One of the first radar devices developed during world war II used microwave radiation of a wavelength that triggers the rotation of water molecules. This was an unfortunate coincidence because

Answer 18

absorption of microwave radiation by water in atmosphere interferes with the detection of intended objects

Question 19

When a given molecule absorbs a photon of microwave radiation,

Answer 19

it begins to rotate.

Question 20

Planck theory of light?

Answer 20

Light contains bundles of energy; the shorter the wavelength of light, the higher the energy of the bundles

Question 21

According to the results of Einstein’s Photoelectric effect experiment

Answer 21

there is a threshold frequency; at higher frequency, photoelectrons are produces while at lower frequency they are not

Question 22

Largest number of moles

Answer 22

smallest atomic weight

Question 23

Uncertainty principle

Answer 23

It is impossible to simultaneously know the exact position and exact momentum for any object

Question 24

The quantum mechanical approach to atomic pressure permits the calculation of

Answer 24

a region about the nucleus in which an electron of specified energy will probably be found

Question 25

If one electron in an atom is excited but does not have enough energy to escape..

Answer 25

then the energy of the excited electron must have one of a set of quantized values