Chapter 12 self-built study guide

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

A period is each horizontal row, there are 7 periods. A group is each each vertical column, there are 18 groups.

Distinguish between an atom and an element.

An atom is made of smaller, subatomic particles - electrons, protons, and neutrons. Elements are any material made of only one type of atom.

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

Because the atom has 43 protons and 43 electrons, it would be Technetium, #43 on the periodic table by adding its #neutrons and protons together you could calculate that the approx. atomic weight is 99 amu (43+56=99). However, you could find the approximate atomic weight on the periodic table too, which would be 98 amu .

Do atoms really consist of shells that actually look like shells?

No. The shell model is not a depiction of the "appearance of an atom." Rather, its a conceptual model that allows us to account for observed behavior. An atom, therefor, does not actually contain a series of concentric shells; it merely behaves as though it does.

What is at the center of every atom?

Protons and neutrons are bound together at the atom's center to form a larger particle - the atomic nucleus.

How many protons are there 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. All atoms that have 26 protons are iron atoms.

What role does the atomic number play in the periodic table?

The modern periodic table lists the elements in order of increasing atomic number.

Does the periodic table explain the shell model, or does the shell model explain the periodic table?

The shell model helps us to understand the organization of the periodic table. It builds a strong foundation for understanding how atoms form chemical bonds.

What is the relationship between the maximum number of electrons each shell can hold and the number of elements in each period of the periodic table?

A series of seven such concentric shells accounts for the seven periods of the periodic table. Furthermore, the number of elements in each period is equal to the shell's capacity for electrons. (ex: the first shell has the capacity for only two electrons. That's why we find only two elements, hydrogen and helium, in the first period.)

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

Carbon dioxide's chemical formulae is CO2, and waters chemical formulae is H2O. If you look at the periodic table you will find a number called the mass number. This is the mass of that particular element. To find the mass of a compound such as carbon dioxide or water you simple add up the mass numbers of each individual element within that compound. So for CO2 you add 12(for carbon,C) and 16(for oxygen,O) and again another 16 (for the 2nd oxygen) you get 44 for the total mass of carbon dioxide. If you now do the same for water adding 1, 1 and 16 you get a total mass number of 18. 44 is higher than 18 therefore carbon dioxide is the heavier compound

The elements copper, Cu; silver, Ag; and gold, Au, are three of the few metals that can be found naturally in there 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 that 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 suggests they should have similar - though not identical - properties.

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

In any one period, all atoms too 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.

Distinguish between mass number and atomic mass.

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.