1. Divided into Groups (vertical columns)
1.1. Down a group, from top to bottom:
1.1.1. Atomic radius increases
1.1.1.1. As there are more electron shells between the nucleus and valence electrons, the screening effect on the valence electrons increases, thus decreasing the force of attraction between the nucleus and the electrons.
1.1.2. Ionization energy decreases
1.1.2.1. For the same reason as increasing atomic radius, less energy is required to remove a valence electron.
1.2. Elements in the same group have similar chemical and physical properties
1.2.1. e.g. They have similar electron configurations.
1.2.2. e.g. All elements in Group VII (halogens) are highly reactive. Reactivity is how easily an element loses or gains electrons from other elements.
1.2.2.1. Elements with a higher reactivity displaces the one with lower reactivity in a compound
2. Divided into Periods (horizontal rows)
2.1. Across period, from left to right:
2.1.1. Elements transition from Metals to Non-metals
2.1.2. Atomic radius decreases
2.1.2.1. The number of protons in the nucleus increases, thus the nuclear charge increases while the increase in screening effect remains negligible, increasing the force of attraction between the nucleus and the electrons.
2.1.3. Ionization energy increases
2.1.3.1. For the same reason as decreasing atomic radius, more energy is required to remove a valence electron.
3. Made up of elements
3.1. All elements are reactive to a certain extent. Reactivity is how easily an element loses or gains electrons from other elements.
3.1.1. When two or more elements react with one another, they may form compounds
3.1.1.1. Ionic compounds: formed when one element transfers electrons to the other, thus becoming ions which are held together by strong ionic bonds to form a lattice structure
3.1.1.1.1. Usually formed when metals bond with non-metals
3.1.1.2. Covalent compounds: formed when elements share electrons when bonding
3.1.1.2.1. Usually formed when non-metals bond with non-metals
3.1.1.2.2. Due to electronegativity: the measure of how much an element pulls electrons away from other elements it is bonded to
4. Arranged in elements (single substance) of ascending atomic number
4.1. Have different chemical and physical properties
4.2. Made up of:
4.2.1. Electron shell
4.2.1.1. Valence shell
4.2.1.1.1. Valency is the number of valence electrons an element has
4.2.1.2. Inner shell
4.2.2. Electrons
4.2.3. Protons
4.2.4. Nucleus