Trends of the Periodic Table

It is very important that you can use the periodic table to distinguish metals from nonmetals. Find the dark jagged line on the Periodic Table On the left side of this line are all of the metals On the right side of this line are all of the nonmetals

The elements that lay on either side of the dark, jagged have rather unique properties. Sometimes they behave like metals, and sometimes they behave like nonmetals. Because of this, they are called Metalloids

Think about counting from the outside to the inside! You need to understand the pattern of elements gaining and donating electrons on the periodic table. Does NOT gain or lose donate 1 electron gains 2 electrons gains 1 electrons donate 2 electron Think about counting from the outside to the inside!

There are several groups/families on the periodic table whose name you should have memorized. Group 1 = Alkali Metals Group 2 = Alkaline Earth Metals Group 17 = Halogens Group 18 = Noble Gases Noble Gases Alkali Metals Halogens Alkaline Earth Metals

The metals in the middle of the periodic table are known as the transition metals.

The Periodic Table can be used to determine the charge of the representative elements when they become ions! +1 +4 or -4 +2 +3 -3 -2 -1 7

Ionic compounds are ALWAYS between a metal and a nonmetal. On the left side of this line are all of the metals On the right side of this line are all of the nonmetals

Covalent compounds are ALWAYS between nonmetals. Covalent compounds occur because nonmetals can also share electrons with other nonmetals On the right side of this line are all of the nonmetals

Part of the way the periodic table is arranged is based on which sublevels are in the outer energy level of each elements atoms. p s d f

Atomic Radius As we discussed, atoms are not spheres. However, we use the term radius to describe the distance from the nucleus to the outermost electron. Just like you would expect, the radius of atoms increases with each additional energy level. This means that the atoms get larger as you go down a group.

Atomic Radius The attractive force between the positive protons and the negative electrons also affects the atomic radius. As you go right along a period, protons are added, but the energy level stays the same. This allows the nucleus to pull harder on the electrons and shrinks the radius of the atoms.

Atomic Radius To remember this trend, remember that cesium has the largest atomic radius. How does atomic radius change as you move down a group and across a period? Elements get larger as you travel down a group. Elements get smaller as you go right across a period.

- 2 When atoms become ions, they gain or lose electrons. This makes the size of ions different from the size of the original atoms. Oxygen + 1 Ionic Radius is the distance from nucleus to the outermost electron in an ion. Sodium

You need to understand how becoming an ion affects the size of metals and the size of nonmetals. Metals lose/donate electrons to become cations. This allows the nucleus to pull even harder on fewer outer electrons. This means metal ions are smaller than the original atoms. Nonmetals gain/accept electrons to become anions. This increases the negative charge in the outer energy level. This means nonmetal ions are larger than the original atoms.

Ionization Energy Ionization energy is the amount of energy required to remove one electron. This definition is VERY important. It is not the energy required to become an ion, it is the energy required to remove 1 electron. Nonmetals tend to GAIN electrons, not lose them. To remove an electron from a nonmetal requires a large amount of energy!

To remember this trend, remember that helium has the greatest ionization energy. How does ionization energy change as you move down a group and across a period? Ionization energy goes down travel down a group. Ionization energy goes up as you go right across a period.

Electronegativity Electronegativity tells you how hard an atom will pull on electrons in a covalent bond. As we will learn, this is what makes some molecules polar.

To remember this trend, remember that fluorine has the greatest electronegativity. How does electronegativity change as you move down a group and across a period? Electronegativity goes down as you go down a group. Electronegativity goes up as you go right across a period.