P199 HW CH 12

Boron has primarily two isotopes, one with an atomic mass of 11 amu and another with an atomic mass of 10 amu. If the abundance of the boron atom with a mass of 11 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?

10.19 amu

If a neutral element has 8 neutrons and 7 electrons, which expression correctly identifies the element?

15/7 N

The nucleus of an electrically neutral iron atom contains 26 protons. How many electrons does this iron atom have?

26

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

If a neutral element has the following chemical symbol, how many electrons does it have? O

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

An element found in another galaxy exists as two isotopes. If 80.0 percent of the atoms have an atomic mass of 80.00 atomic mass units and the other 20.0 percent have an atomic mass of 82.00 atomic mass units, what is the atomic mass of the element?

80.4 atomic mass units

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

9

If a neutral element has the following chemical symbol, how many electrons does it have? U

92

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.

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

Where did the atoms that make up a newborn baby originate? A. In the digestion of the food that the mother B. In the explosions of ancient . C. In the womb of the baby's mother. D. In the Earth through geological processes.

In the explosions of ancient .

If you remove two protons and two neutrons from a gold atom (Au), what new element is formed (if any)?

Ir

Since atoms are mostly empty space, why don't objects pass through one another? A. The electrons on the atoms repel other electrons on other atoms when they get close. B. The electrons of one attract the nucleus of a neighboring atom to form a barrier. C. The nucleus of one atom repels the nucleus of another atom when it gets close. D. The nucleus of one atom attracts the nucleus of a neighboring atom to form a barrier.

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

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.

How do we account for the great variety of substances in the world? A. There are many possible combinations of atoms. B. The Earth is 4.5 billion years old. C. Most of these substances are organic compounds. D. Atoms are incredibly small.

There are many possible combinations of atoms.

Which are older, the atoms in the body of an elderly person or those in the body of a baby? A. An elderly person because they have been around much longer. B. It depends upon their diet. C. A baby because this is surely a trick question. D. They are of the same age, which is appreciably older than the solar system.

They are of the same age, which is appreciably older than the solar system.

In what sense can you truthfully say that you are a part of every person around you? A. There are more people alive now than have ever lived. B. We all live on the same planet and share the same resources. C. We are continually exchanging our atoms. D. We all share the same genetic code.

We are continually exchanging our atoms.

Does it make sense to say that a textbook is about 99.9 percent empty space? A. Yes. A textbook like all material things is made up of atoms, which are considered to be 99.9 percent empty space. B. No. Only gases are considered to be 99.9 percent empty space. Liquids and solids are not. C. No. A textbook could only be considered to be 99.9 percent empty space if it were combusted. D. No. A textbook is a solid and thus is quite dense. Therefore it is not 99.9 percent empty space.

Yes. A textbook like all material things is made up of atoms, which are considered to be 99.9 percent empty space.

Which has more atoms: a 1-gram sample of carbon-12 or a 1-gram sample of carbon-13?

a 1-gram sample of carbon-12

Which of the following statements best describes an element? A. a material that is pure B. a material that has consistent physical properties C. a material that has consistent chemical properties D. a material with more than one type of atom E. a material consisting of only one type of atom

a material consisting of only one type of atom

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

a uranium atom with 92 protons and 146 neutrons

What does the following element description actually mean? 16 8 O

an oxygen atom with 6 protons and 12 neutrons

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

argon-38

If an atom has 43 electrons, 56 neutrons, and 43 protons, what is its approximate atomic mass? What is the name of this element?

atomic mass, 99 amu; Technetium

You could swallow a capsule of germanium, Ge (atomic number 32), without significant ill effects. If a proton were added to each germanium nucleus, however, you would not want to swallow the capsule because the germanium would

become arsenic.

Rank the three subatomic particles in order of increasing mass: (a) neutron, (b) proton, (c) electron.

c,a,b

If two protons and two neutrons are removed from the nucleus of an oxygen atom, a nucleus of which element remains?

carbon-12

Which contributes more to an atom's size?

electrons

If an element has 10 protons and 11 neutrons and 10 electrons, which expression correctly identifies the element?

neon-21

Which contributes more to an atom's mass: electrons or protons?

protons

Using the following generic atom description, choose the correct method for determining the number of neutrons. F G X

subtract G from F

Considering how small atoms are, what are the chances that at least one of the atoms exhaled in your first breath will be in your last breath? A. not possible at all because atom don't last that long B. very probable because of how incredibly small atoms are C. not very likely because atoms are constantly dematerializing D. There's not really a way that scientists are able to make such an estimate.

very probable because of how incredibly small atoms are

Which is heavier: a water molecule, H2O, or a carbon dioxide molecule, CO2?

CO2

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? A. Neutrons travel at reduced speed compared to the speed at which protons travel. B. Neutrons carry no electric charge and thus have a greater likelihood of passing through the tissue. C. Neutrons are much smaller and lighter than protons and would do less damage. D. All of the above are reasons why neutrons are less harmful.

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

If all the molecules of a body remained part of that body, would the body have any odor? A. Yes, because it would still release photons. B. No, because it would no longer be what it was. C. No, because there would be no molecules traveling to our nose. D. Yes, but only if that body is sweating.

No, because there would be no molecules traveling to our nose.

Which contributes more to an atom's mass: electrons or protons? Which contributes more to an atom's size?

Protons contribute more to an atom's mass while electrons contribute more to its size.

If you remove two protons and two electrons from a sulfur atom (S), what new element is formed?

Si

When we breathe we inhale oxygen, O2, and exhale carbon dioxide, CO2, plus water vapor, H2O. Which likely has more mass, the air that we inhale or the same volume of air we exhale? Does breathing cause you to lose or gain weight?

The air we exhale has more mass; Breathing causes you to lose weight.

Why are the atomic masses listed in the periodic table not whole numbers?

The atomic masses are average atomic masses.

A cat strolls across your backyard. An hour later, a dog with its nose to the ground follows the trail of the cat. Explain what is going on from a molecular point of view. A. The dog is smelling atoms from the cat B. The dog is smelling molecules from the cat. C. The cat is leading the dog into a trap. D. The dog is following the areas of increased density of the Earth.

The dog is smelling molecules from the cat.