Midterm Review Chapter 4 Periodic Table

Dmitri Mendeleev Father of the periodic table

Periodic Table The periodic table is arranged off of the periodic law Periodic Law – repeating physical and chemical properties of elements change periodically with their atomic number

Valence Electrons Valance electrons are the electrons in the outermost energy level The number of valence electrons in an atom corresponds to the group number on the periodic table – Group 1 elements all have 1 valence electrons – Group 2 elements all have 2 valence electrons

Valence Electrons This changes for groups Instead of group 13 having 13 valence electrons, they only have 3 Group 14 has 4 valence electrons

Valence Electrons Valence electrons predict reactivity of elements Octet Rule – atoms tend to have either empty valence shells or full valence shells of eight electrons – Exceptions – Hydrogen (H) and Helium (He) because they are in the first energy level

Valence Electrons If an atom only needs to gain or lose 1 valence electron, the atom is very unstable. – Alkali Metals (group 1) – Halogens (group 17) If an atom needs to gain or lose 2 valence electrons, it is more stable than the first example but still unstable – Alkaline Earth Metals (Group 16)

Valence Electrons Noble Gases – are considered stable because they have full outer energy levels (8 valence electrons)

For the Midterm pg Know the positions on the periodic table for the following: – Main-group element – Alkali metal – Alkaline-Earth Metal – Halogen – Noble Gas – Transition Metal

Trends in the Periodic Table pg Ionization Energy – the energy required to remove an electron from an atom or ion

Electron Shielding Electron shielding – charge of nucleus on outermost electrons is blocked by other electrons surrounding the nucleus This concept plays a role in understanding the trend in ionization energy across the periodic table

Electronegativity Electronegativity – a measure of the ability of an atom in a chemical compound to attract electrons