3A+Krystal



The Periodic Table is a tabular display of the chemical elements, organized on a basis of their properties. The elements are presented in increasing atomic number in groups or periods. This is to keep the elements with similar properties together, such as the halogens and the metals. The Periodic Table is divided into different sections based on the properties of the elements. The Periodic Table is split into 7 different periods (rows) and 18 different groups (columns). As well as being split into the groups and periods, the Periodic Table is also divided into different sections based on the properties of the elements. The table is divided into metals and non-metals. It is then further divided into Alkali Metals, Alkaline Earth Metals, Transition Metals, and Post-Transition Metals, under the metals section. The metals section is then followed by the Metalloids. After the Metalloids, are the non-metals which consist of the other non-metals, Halogens, and Noble gases. Following the non-metals section are the elements with unknown chemical properties. Underneath this are the inner transition metals, Lanthanides or Lanthanoids and Actinides or Acinoids. (Shown in Figure 1.0)

Figure 1.0: Periodic Table showing different sections

Since the development of the periodic table by Dmitri Mendeleev in 1869, scientists have discovered many different trends within it. included in these trends is the trend of the First Ionisation Energy.

Ionisation Energy is the energy required to remove electrons from gaseous atoms or ions. The energy needed to remove the first electron from the outer shell is called the First Ionisation Energy. As you go across the Periodic Table the First Ionisation Energy increases and as you go down the table, the First Ionisation Energy decreases. (Refer to Figure 1.1) Figure 1.1: First Ionisation Energy Trends The First Ionisation Energies of the elements decreases down a group. This can be seen for the elements in group 1 and group 17 as shown in figure 1.2

Figure 1.2 Decrease in Ionisation Energy The decreases in the First Ionisation Energy down a group can be explained in terms of the distance from the nucleus of the electron being removed. The further from the nucleus the outermost electron is, the less attraction there is between the electrons and the nucleus. Less energy will therefore be required to remove the outermost electron. Going down a group on the Periodic Table, the differences in the First Ionisation Energies of the elements is mainly due to the different distances between the nucleus and the outermost electron being removed during the ionisation process.

Going across a period on the Periodic Table the general trend is for the First Ionisation Energy to increase. Moving from one element to the next across a period, an additional proton is added to the nucleus, which increases the core charge. Therefore, the electrons in the outermost shell with have a stronger attraction to the nucleus. As a result of this, it will require more energy to remove an electron from the atoms with the larger atomic number in a particular period. For and example of this, refer to Figure 1.3.

Figure 1.3: The First Ionisation Energies of elements from the first four periods of the Periodic Table

[] [] [] Chemistry for WA 2, Stage 3: Units 3A and 3B by Cherie Lewis and Peter Lewis.
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