CHEM 1010 CHPT 4 - FARRELLY

Boron has primarily two isotopes, one with an atomic mass of 11.0 amu and another with an atomic mass of 10.0 amu. If the abundance of the boron atom with a mass of 11.0 amu is 18.9 percent and the abundance of the other isotope is 81.1 percent, what would be the average mass of the boron atom?

10.2 amu

If an element has 15 protons and 16 neutrons and 15 electrons, what is the atomic mass of the element?

31

If a neutral element has the following chemical notation, how many electrons does it have? carbon-13

6

The isotope lithium-7 has a mass of 7.0160 atomic mass units, and the isotope lithium-6 has a mass of 6.0151 atomic mass units. Given the information that 92.58 percent of all lithium atoms found in nature are lithium-7 and 7.42 percent are lithium-6, calculate the atomic mass of lithium, Li (atomic number 3).

6.942 amu

Visible light has a frequency range between 7 × 1014 Hz and 4 × 1014 Hz. Which frequency of light would have the most energy?

7 × 1014 Hz

If a neutral element has the following chemical notation, how many electrons does it have? fluorine-19

9

What is the approximate mass of a carbon atom in atomic mass units (amu)? How about a carbon dioxide molecule?

A carbon atom has a mass of about 12 amu. Carbon dioxide would then have a mass of 44 amu.

Which of the following could best be represented by a physical model?

A) a cell

Which of the following statements is false?

An atom emits electromagnetic radiation when an electron moves from a lower energy level to a higher energy level.

How is it possible to deduce the identity of an element from its electron configuration?

An electron configuration is unique to each element, much like its atomic spectrum.

Which of the following atoms is the smallest?

Br

The element bromine, Br (atomic number 35), has two major isotopes of similar abundance, both around 50 percent. The atomic mass of bromine is reported in the periodic table as 79.904 atomic mass units. Choose the most likely set of mass numbers for these two bromine isotopes.

Br-79, Br-81

Which of the following experiments helped to determine that most of an atom is actually empty space except for a very small positive core?

E. Rutherford's gold foil experiments

Which element has the atomic number 9?

F

Which of the following atoms is the smallest?

F

Which of the following gases would diffuse the fastest through an extremely fine membrane?

He

Which element has the atomic number 12?

Mg

A beam of protons and a beam of neutrons of the same energy are both harmful to living tissue. The beam of neutrons, however, is less harmful. Why?

Neutrons carry no electric charge and thus have a greater likelihood of passing through the tissue.

Since atoms are mostly empty space, why don't objects pass through one another?

The electrons on the atoms repel other electrons on other atoms when they get close.

Which of the following statements is true about Bohr's planetary model of the atom?

The electrons orbit around the nucleus.

An element has two different isotopes: one that weighs 65 amu and another that weighs 67 amu. If the average atomic mass of all the isotopes is 66.5 amu, what can be said about the relative abundance of the isotopes?

The isotope with the mass of 67 is more abundant than the isotope with the mass of 65.

Evidence for the existence of neutrons did not come until many years after the discoveries of the electron and the proton. Give a possible explanation.

The neutron lacks an electrical charge.

The shell model presented in this book is not very accurate. Why then is it presented?

The shell model is simpler, useful and easy to understand.

Which of the following might best explain the reason why electrons are restricted to certain energy levels in an atom?

They behave like restricted waves and are self-reinforcing.

Which of the following best describes a conceptual model of an atom?

a model that illustrates the tendency of an atom to undergo radioactive decay and the products it produces

What does the following element description actually mean? 92U-238

a uranium atom with 92 protons and 146 neutrons

Which of the following is a property of light? (A) It is a wave. (B) It is a particle. (C) Its energy comes in packets of uniform size. (D) all of the above

all of the above

Which of the following statements about electrons is true? (A) Electrons have a negative charge. (B) Electrons are particles. (C)Electrons behave like waves. (D) Electrons in atoms can be excited by light energy. (E) all of the above

all of the above

If an element has 18 protons and 20 neutrons and 18 electrons, which expression correctly identifies the element?

argon-38

Which of the following is not a property of an electron?

charge changes depending on mass

Another interesting periodic trend is the density of the elements. We find that osmium, Os (atomic number 76) has the greatest density of all elements, and, with some exceptions, the closer an element is positioned to osmium, the greater its density. Based upon this trend, list the following elements in order of increasing density: copper, Cu, gold, Au, platinum, Pt, and silver, Ag.

copper, Cu < silver, Ag < gold, Au < platinum, Pt

Which of the following concepts underlies all the others: ionization energy, effective nuclear charge, atomic size.

effective nuclear charge

The ________ represents the complete range of frequencies of light energy from radio waves to gamma rays.

electromagnetic spectrum

Which of the following statements describes an isotope?

element with the same number of protons but a different number of neutrons

Rank the following by relative frequency from highest to lowest:

gamma rays, blue light, red light, radio waves

What does the following element description actually mean? iron-57

iron with a mass number of 57

An atomic orbital ________.

is a region of space where an electron is most likely to be found

An electron in an outermost shell has more energy than one in an innermost shell because ________.

it is farther from the nucleus

Isotopes of the same element have a different number of ________.

neutrons

Rutherford assumed that the atomic nucleus was positively charged because ________.

the alpha particles that ricocheted off of the nucleus are also positively charged

Which of the following is said to be quantized?

the number of eggs in an egg carton

The mass number of an element is ________.

the sum of the protons and the neutrons

Oxygen, O, (number 8), sulfur, S, (number 16), and selenium, Se, (number 34) have such similar chemical properties because ________.

their outermost shells contain the same number of electrons

In Rutherford's gold foil experiment, alpha particles ________.

were deflected by the atomic nucleus

Which of the following could NOT be represented by a conceptual model?

(A) the energy of a nucleus

The following statement describes which subatomic particle best? It is a nucleon. (A) an electron (B) a proton (C) a neutron (D) B and C

(D) B and C

The following statement describes which subatomic particle best? It has a relatively large mass. (A) an electron (B) a proton (C) a neutron (D)A and B (E) B and C

(E) B and C

The following statement describes which subatomic particle best? It is located outside of the nucleus.

(A) an electron

List the following atoms in order of increasing atomic size: Thallium, Tl; Germanium, Ge; Tin, Sn; Phosphorus, P.

P < Ge < Sn < Tl

How does Rutherford's model of the atom explain why some of the alpha particles directed at the gold foil were deflected straight back toward the source?

The atomic nucleus is very small but dense and carries a positive electric charge.