CHAPTER 12: Atoms and the Periodic Table

How many periods are in the periodic table? How many groups?

7 periods 18 groups

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

80.4 amu

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

99 amu; technetium

Atomic Number

A count of the number of protons in the atomic nucleus.

Period

A horizontal row in the periodic table.

Conceptual Model

A representation of a system that helps us predict how the system behaves.

Group

A vertical column in the periodic table, also known as a family of elements.

What must an electron be doing in order to have wave properties?

According to de Broglie, particles of matter behave like waves by virtue of their motion. An electron must therefore be moving in order to have wave properties. In atoms, electrons move at speeds of about 2 million m/s, and so their wave nature is most pronounced.

How might you deduce the elemental composition of a star?

Aim a well-built spectroscope at a star and study its spectral patterns. In the late 1800's, this was done with our own star, the Sun. Spectral patterns of hydrogen and some other known elements were observed, in addition to one patter that could not be identified. Scientist concluded that this unidentified pattern belonged to an element not yet discovered on Earth. They named this element helium after the Greek word for "sun", helios.

Neutron

An electrically neutral subatomic particle of the atomic nucleus.

Electron

An extremely small, negatively charged subatomic particle found outside the atomic nucleus.

Why are atoms invisible?

An individual atom is smaller than the wavelengths of visible light and so is unable to reflect that light. Atoms are invisible, therefore, because visible light passes right by them. The atomic images generated by scanning probe microscopes are not photographs taken by a camera. Rather, they are computer renditions generated from the movements of an ultra-thin needle.

Element

Any material that is made3 up of only one type of atom.

Nucleon

Any subatomic particle found in the atomic nucleus; another name for either a proton or a neutron.

Distinguish between atomic number and mass number.

Atomic number is the amount of protons in the nucleus. The mass number is the total number of protons and neutrons.

What causes an atom to emit light?

Atoms emit light when they undergo energy.

Distinguish between mass number and atomic mass.

Both terms include the word mass and so are easily confused. Focus your attention on the second word of each term,however, and you'll get it right every time. Mass number is a count of the number of nucleons in an isotope. An atom's mass number requires no units because it is simply a count. Atomic mass is a measure of the total mass of an atom, which is given in atomic mass units.

Which element has chemical properties the most similar to chlorine (Cl, atomic number 17)?

Br

The elements copper, Cu; silver, Ag; and gold, Au, are three of the few metals that can be found naturally in their elemental state. These three metals have found great use as currency and jewelry for a number of reasons, including their resistance to corrosion and their remarkable colors. How is the fact and these metals have similar properties reflected in the periodic table?

Copper (atomic number 29), silver (atomic number 47), and gold (atomic number 79) are all in the same group in the periodic table (group 11), which suggest they should have similar-though not identical-properties.

The isotope lithium-7 has a mass of 7.0160 amu, and the isotope lithium-6 has a mass of 6.0151 amu. Given that 92.58% of all Lithium atoms found in nature are lithium-7 and 7.42% are lithium-6, show that the atomic mass of lithium, is 6.941 amu.

Li-7 = .9252 x 70.16 = 6.495 LI-6 = .07 x 6.0151 = .0446 6.495 .0446 = 6.941

Which are larger: atoms of cesium, CS (atomic number 55), or atoms of radon, Rn (atomic number 86)?

Look at the trends and you'll see that, in any one period, all atoms to the left are larger than those to the right. Accordingly, cesium is positioned at the far left of period 6, and so you can reasonably predict that its atoms are larger than those of radon, which is positioned at the far right of period 6. The periodic table is a road map to understanding the elements.

Isotopes

Members of a set of atoms of the small element whose nuclei contain the same number of protons but different numbers of neutrons.

Are most elements metallic or nonmetallic?

Metallic.

List the following atoms in order of increasing atomic size: thallium, TI; germanium, Ge; tin,Sn; phosphorus,P.

P>Ge>Sn>TI

Which has more energy: a photon of red light or a photon of infrared light?

Red light is higher frequency than infrared light, which means a photon of red light has more energy than an photon of infrared light. Recall that photon is a single discrete packet (a quantum) of radiant energy.

Is the Bohr model of atom a physical model or a conceptual model?

The Bohr model is a conceptual model. It is not a scaled-up version of an atom, but instead is a representation that accounts for the atom's behavior.

Atomic Symbol

The abbreviation for an element or atom.

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

The atomic mass is 99. The name of this element is Technetium.

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

The atomic mass is contributed by protons. The atom's size is contributed by electrons.

Distinguish between mass number and atomic mass.

The atomic mass measures the total mass of an atom. The mass number is the total number of protons and neutrons in an isotope.

Why aren't the atomic masses given in the periodic table whole numbers?

The atomic masses are average atomic masses.

Why aren't the atomic masses listed in the periodic table whole numbers?

The atomic masses are average variety of isotopes that are in an element.

How many protons are in an iron atom, Fe (atomic number 26)?

The atomic number of an atom and its number of protons are the same. Thus, there are 26 protons in an iron atom. Another way to put this is that all atoms that contain 26 protons are, by definition, iron atoms.

What does a spectroscope do to the light coming from an atom?

The color of each element is revealed and displays a pattern of distinct frequencies.

Atomic Nucleus

The dense, positively charged center of every atom.

Atomic Mass

The mass of an element's atoms listed in the periodic table as an average value based on the relative abundance of the element's isotopes.

Atomic Spectrum

The pattern of frequencies of electromagnetic radiation emitted by the atoms of an element, considered to be an element's "fingerprint."

A basketball coach describes a playing strategy to her team by way of sketches on a game board. Do the illustrations represent a physical model or a conceptual model?

The sketches are a conceptual model the coach uses to describe a system (the players on the court), with the the hope of predicting an outcome (winning the game).

Which are older: the atoms in the body of an elderly person or atoms in the body of a baby?

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

How does the wave model of electrons orbiting the nucleus account for the fact that the electrons can have only discrete energy values?

When an electron wave is confined, it is reinforced at only particular frequencies.

A friend claims there are atoms in his brain that were once in the brain of Albert Einstein. Is your friend's claim likely correct or nonsense?

Your friend is correct! In addition, there are atoms in your friend's and everyone else's body that were once part of Einstein and everybody else, too! There arrangements of these atoms, however, are now quite different. What's more, the atoms of which you and your friend are composed will be found in the bodies of all the people on Earth who are yet to be.

Consider these atoms: helium, aluminum, argon. Rank them, from smallest to largest in terms of... a. size b. number of protons in the nucleus c. number of electrons

a. Helium, Argon, Aluminum b. Helium, Aluminum, Argon c. Helium, Aluminum, Argon

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.

How many electrons are in the third shell of sodium, Na (atomic number 11)?

one

Would you use a physical model or conceptual model to describe the following: the brain, the mind, the solar system, the beginning of the universe?

physical, conceptual, physical , conceptual