The number of protons is the same as the atomic number, so the atom is oxygen. Have groups work together to place each card with its correct atom. Discuss the placement of the cards for two or three atoms. Explore Project the Periodic table of energy levels and discuss the arrangement of electrons as students complete their activity sheet. Tell students that the rows across on the periodic table are called periods.
Period 1 Hydrogen Explain that hydrogen has 1 proton and 1 electron. The 1 electron is on the first energy level. Helium Explain that helium has 2 protons and 2 electrons. The 2 electrons are on the first energy level. Period 2 Lithium Explain that lithium has 3 protons and 3 electrons. There are 2 electrons on the first energy level and 1 electron on the second.
Explain that the first energy level can only have 2 electrons so the next electron in lithium is on the next second level. Neon Explain that neon has 10 protons and 10 electrons. There are 2 electrons on the first energy level and 8 electrons on the second level. Beryllium—fluorine Help students fill in the correct number of electrons in the energy levels for the rest of the atoms in period 2.
Period 3 Sodium Explain that sodium has 11 protons and 11 electrons. There are 2 electrons on the first energy level, 8 electrons on the second level, and 1 electron on the third energy level. Explain that the second energy level can only have 8 electrons so the next electron in sodium has to be on the next third level. Argon Explain that argon has 18 protons and 18 electrons.
There are 2 electrons on the first energy level, 8 electrons on the second level, and 8 electrons on the third energy level.
Have students complete the energy level model for argon in their periodic table. Magnesium—chlorine Help students fill in the correct number of electrons in the energy levels for the rest of the atoms in period 3. Period 4 Potassium Explain that potassium has 19 protons and 19 electrons. There are 2 electrons on the first energy level, 8 electrons on the second level, 8 electrons on the third energy level, and 1 on the fourth energy level.
Explain that after the third energy level has 8 electrons, the next electron goes into the fourth level. Calcium Help students fill in the correct number of electrons in the energy levels for calcium. Have students look for patterns in rows and columns of the first 20 elements in the periodic table.
Have students look at the periods rows going across. Number of energy levels in each period The atoms in the first period have electrons in 1 energy level. The atoms in the second period have electrons in 2 energy levels.
The atoms in the third period have electrons in 3 energy levels. The atoms in the fourth period have electrons in 4 energy levels. Have students look at the groups columns going down. Tell students that the vertical columns in the periodic table are called groups or families. Extend Compare the way different elements react chemically and relate this to their location on the periodic table.
Project the video Sodium in water and potassium in water. Project the video Calcium in water. Project the videos Sodium in acid and potassium in acid. Project the video Calcium in acid. Ask students: Do elements in the same group have similar properties and react in similar ways?
Students should realize that sodium and potassium are in the same group and react similarly. Calcium is near them on the periodic table, but is in a different group, so it reacts differently. The second energy level can have eight electrons. The third energy level can have a total of 18 electrons. The fourth energy level can have 32 electrons. According to the Aufbau Principle, electrons will fill the lowest energy levels first and build into the higher levels only if the energy level before it is full.
Each energy level is made up of areas known as an orbital. An orbital is an area of probability in which electrons can be found.
Each energy level, except for the first, has more than one orbital. Each orbital has a specific shape. This shape is determined by the energy the electrons in the orbital possess. Electrons can move anywhere within the shape of the orbital at random.
The characteristics of each element are determined by the electrons in the orbital. The s-orbital is shaped as a sphere.
The s-orbital is always the first to be filled in each energy level. The first two columns of the periodic table are known as the s-block. This means that the valence electrons for these two columns exist in an s-orbital.
The first energy level only contains an s-orbital. For example, hydrogen has one electron in the s-orbital. Ten electrons are needed to fill the five d orbitals, so we start ten columns in this fourth period, placing the columns next to column 2 and between it and column 3. The 4p sublevel is filled next, after the 3d sublevel. The boxes for the elements formed by filling the p orbitals are in place under the boxes for elements formed by adding the 3p electrons.
By consulting Figure 5. Boxes for the elements formed by filling the orbitals of these sublevels are arranged as were those in period 4. Just as period 4 contains more elements than period 3, period 6 contains more elements than period 5. Period 6 starts with elements whose last added electron is in the 6s sublevel. The next step is where period 6 differs from period 5. Look again at Figure 5. We will need 14 boxes to contain the electrons needed to fill the seven f orbitals.
These are the boxes of the lanthanide series, shown below the table. There is some evidence that these orbitals do not fill before one electron is in a 5d orbital, so we have shown in Figure 5.
After the 4f orbitals are filled, boxes are shown for the rest of the elements formed by adding 5d and 6p electrons. The seventh period contains boxes for the elements formed by filling the 7s, the 5f the actinide series shown below the table , and finally the 6d sublevels. This relationship is further expressed by the following names sometimes given to parts of the table: columns 1 and 2 s block columns p block short columns d block lanthanides and actinides f block The groups of elements found in these blocks are also known by other names.
Categories of Elements in the Periodic Table 1. The representative elements Elements in the s and p blocks are known as representative elements or main group elements.
The term representative dates from early times, when chemists believed that the chemistry of these elements was representative of all elements. Group 8 is not always included in the representative elements because the chemistry of the noble gases is unique to them. In period 7 there are no elements in the p block. The p block of period 7 would contain elements with atomic numbers greater than ; such elements have not yet been found in the Earth's crust nor have they been prepared by nuclear reaction.
In the s and p blocks, the period in which the element occurs has the same number as the highest energy level that contains electrons in a ground-state atom. The number of the column in which an element is found is the same as the number of s and p electrons in that level. Sodium is a representative element with 11 electrons. Its electron configuration is: 1s 2 2s 2 2p 6 3s 1. Sodium is in column 1 of the third period. In a sodium atom, the highest-energy principal energy level containing electrons is the third energy level, and that energy level contains one electron.
The transition elements The transition elements or transition metals, for they are all metals are those elements found in the short columns of the d block. Many of these elements are probably familiar to you.
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