The purpose of the of the periodic table is to arrange chemical elements in an organised way in order to simplify things. The development of the modern periodic table started with Dmitri Mendeleev, who in 1869, created the first periodic table, which he arranged by atomic mass, and similar properties. In 1914, Henry Moseley rearranged the periodic table by atomic name but kept Mendeleev's property arrangement.​

The Arrangement of the Periodic Table

Overall, the periodic table is arranged by atomic number, increasing chronologically from left to right. The periodic table has vertical rows called groups. Elements in groups have similar properties, the same valence electron configuration (form the same ions), and as you go down, always one shell is added to the atom. The periodic table has vertical rows called groups, and the lower you go, the more shells an atomic has. Furthermore, the periodic table has horizontal rows called periods. Across a period, the number of shells stays the same but the atomic number increases going right.​

Trends about which you have learned using the periodic table

I have learned about Atomic Radii and Ionization energy.

               Ionization Energy is the energy needed by an atom to remove the outermost, or highest energy, electron from a neutral atom, in order to form a cation. Looking at its trend, Ionization energy decreases going down. This is because the valence electrons are farther away from the nucleus, making it easier to remove them since the nucleus cannot pull them in, meaning little IE is required. Also, IE decreases down due to shielding. Across a period however, it increases going right. This is due to the fact that going right, the atomic number increases. Consequently, across a period there are more electrons / protons at the right. More protons have a stronger pull on electrons and pull them in closer. All the way to the right, more protons hold the electrons stronger, so a stronger energy is required to remove them. Additionally, the more electrons there are in the valence shell, the more energy it takes to remove one. Finally, there are different types of ionization energy. The energy required to remove the first electron is called the “first ionization energy”, the energy required to remove the second electron is called the "second ionization energy" and so on. The higher the electron you need to remove, the higher the ionization energy.The 3rd ionization energy is higher than 1st ionization energy because it always takes more energy to remove an electron from an already charged ion than from a neutral atom.

               The Atomic Radii is a measure of the size of an element’s atom, usually the mean or typical distance from the nucleus to the boundary of the surrounding clouds of e-. Within the same group, the atomic radius increases as you go down. There is an increase in nuclear charge but adding another principal energy level is the dominant factor. The addition of another energy level (shell_ results in the valence electrons being further from the nucleus, since there are more shells, which results in a larger atom. Within the same period, the atomic radius decreases as you move from left to right. This is due to the atomic number increasing, meaning more protons and electrons. This increase in nuclear charge with the number of shells staying constant results in a smaller atomic radius. More protons pull the electrons tighter towards the nucleus decreasing the radius.