Ch 11 Exercises
the atomic masses of two isotopes of cobalt are 59 and 60. (a) what is the number of protons and neutrons in each? (b) what is the number of orbiting electrons in each when the isotopes are electrically neutral?
(a) in both there are 27 protons. there are 32 neutrons in Co-59 and 33 neutrons in Co-60. (b) the number of orbiting electrons matches the atomic number, 27
what is the cause of the Brownian motion of dust particles? what aren't larger objects, such as baseballs, similarly affected?
Brownian motion is the result of more atoms or molecules bumping against one side of a tiny particle than the other. this produced a net force on the particle, which alters its motion. such Brownian motion is not observed for larger particles because the numbers of bumps on opposite sides is more nearly equal, and the inertia of the larger particle is greater. any Brownian motion of a baseball would be imperceptible
if no molecules in a body could escape, would the body have any odor?
a body would have no odor if all its molecules remained within it. a body has odor only if some of its molecules enter a nose
your friend says that what makes one element distinct from another is the number of electrons about that atomic nucleus. Do you agree wholeheartedly, partially, or not at all? explain.
agree partially. it's better to say an element is defined by the number of protons in the nucleus. the number of protons and electrons are equal only when the element is not ionized
if two protons and two neutrons are removed from the nucleus of an oxygen atom, what nucleus remains?
carbon
the atoms that constitute your body are mostly empty space, and structures such as the chair you're sitting on are composed of atoms that are also mostly empty space. so why don't you fall through the chair?
electrical repulsion. electrons speeding around within an atom create an electrified cloud that repels the similar clouds of other electrons, preventing the atoms from coalescing and keeping us from falling through our chairs (quantum effects play a large role as well)
which of the following elements would you predict to have properties most like those of silicon (Si): aluminum (Al), phosphorus (P), or germanium (Ge)?
germanium (Ge), which is in the same column directly below silicon in the periodic table
you could swallow a capsule of germanium without ill effects. but, if a proton were added to each of the germanium nuclei, you would not want to swallow the capsule. Why?
germanium would become arsenic
how many individual atoms are in a water molecule?
in a water molecule, H2O, there are three atoms, two hydrogen and one oxygen
why don't equal masses of carbon atoms and oxygen atoms contain the same number of particles?
individual carbon atoms have less mass than individual oxygen atoms, so equal masses of each means more carbons than oxygens
why don't equal masses of golf balls and ping-pong balls contain the same number of balls?
individual ping-pong balls are less massive than individual golf balls, so equal masses of each means more ping-pong balls than golf balls
what element results if you add a pair of protons to the nucleus of mercury?
lead
a hydrogen atom and a carbon atom move at the same speed. which has the greater kinetic energy?
letting the formula KE=1/2mv2 guide your thinking, for the same speed the atom with greater mass has greater KE. greater-mass carbon therefore has greater KE than hydrogen for the same speed
how many atoms are in a molecule of ethanol, C2H6O?
nine
which of the following are pure elements: H2, H2O, Hc, Na, NaCl, H2SO4, U?
of the substances listed, H2, He, Na, and U are pure elements. H2O and NaCl are compounds made of two elements, and three different elements contribute to H2SO4
how many types of atoms can you expect to find in a pure sample of any element?
one (although perhaps more than one isotope)
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, and electrons more to an atom's size
what element results if two protons and two neutrons are ejected from a radium nucleus?
radon
a carbon atom, with a half-full outer shell of electrons- four in a shell that can hold eight- readily shares its electrons with other atoms and forms a vast number of molecules, many of which are the organic molecules that form the bulk of living matter. looking at the periodic table, what other element do you think might play a role like carbon in life forms on some other planet?
silicon, which is in the same group
which contains more atoms: 1 kg of lead or 1 kg of aluminum?
since aluminum atoms are less massive than lead atoms, more aluminum atoms than lead atoms compose a 1 kg sample
somebody told your friend that if an antimatter alien ever set foot upon earth, the whole world would explode into pure radiant energy. your friend looks to you for verification or refutation of this claim. what do you say?
the amount of matter that a given amount of antimatter would annihilate is the same as the amount of antimatter, a pair of particles at a time. the whole world could not be annihilated by antimatter unless the mass of antimatter were at least equal to the mass of the world
where were the atoms that make up a newborn infant "manufactured"?
the atoms that make up a newborn baby or anything else in this world originated in the explosions of ancient stars. the molecules that make up the baby, however, were formed from atoms ingested by the mother and transferred to her womb
when a container of gas is heated, what happens to the average speed of its molecules?
the average speed of molecules increases
a cat strolls across your backyard. an hour later, a dog with his nose to the ground follows the trail of the cat. explain this occurrence from a molecular point of view.
the cat leaves a trail of molecules and atoms on the grass. these in turn leave the grass and mix with air, where they enter the dog's nose, activating its sense of smell
a particular atom contains 29 electrons, 34 neutrons, and 29 protons. what is the identity of this element and its atomic number?
the element is copper, atomic number 29. any atom having 29 protons is by definition copper
in a gaseous mixture of hydrogen and oxygen gas, both with the same average kinetic energy, which molecules move faster on average?
the hydrogen molecules, having less mass, move faster than the heavier oxygen molecules
helium is an inert gas, meaning that it doesn't readily combine with other elements. what five other elements would you also expect to be inert gases?
the other inert gases are neon, argon, krypton, xenon, and radon
the average speed of a perfume-vapor molecule at room temperature may be about 300 m/s, but you'll find the speed at which the scent travels across the room is much less. Why?
the speed at which the scent of a fragrance travels is much less than the speed of the individual molecules that make it up because of the many collisions among molecules. although the molecular speed between collisions is great, the rate of migration in a particular direction through obstructing molecules is very much less
hydrogen and oxygen always react in a 1:8 ratio by mass to form water. early investigators thought this meant that oxygen was 8 times more massive than hydrogen. what chemical formula did these investigators assume for water?
they assumed that a water molecule is made of one hydrogen atom and one oxygen atom, HO
to become a negative ion, does an atom lose or gain an electron?
to become negative, gain an electron
to become a positive ion, does an atom lose or gain an electron?
to become positive, lose an electron
which of the following is not an element: hydrogen, carbon, oxygen, water?
water is not an element. it is a compound. its molecules are made of the atoms of elements hydrogen and oxygen
what are the chances that at least one of the atoms exhaled by your very first breath will be in your next breath?
with every breath of air you take, it is highly likely that you inhale one of the atoms exhaled during your very first breath. this is because the number of atoms of air in your lungs is about the same as the number of breaths of air in the atmosphere in the world
in what sense can you truthfully say that you are a part of every person in history? in what sense can you say that you will tangibly contribute to every person on earth who will follow?
you really are a part of every person around you in the sense that you are composed of atoms not only from every person around you, but from every person who has ever lived on earth. the child's statement in the part 2 photo opener is indisputable. and the atoms that now compose you will make up the atomic pool that others will draw upon
