Electron Configurations and the Periodic Table • The periodic table is arranged by how the electrons within an atom fill orbitals. • The periodic table is broken into blocks according to how the electron configuration of an atom ends. • s-block • Configurations end in s1 or s2 • Composed of groups 1 and 2 • Group 1 called alkali metals (except H) • Group 2 known as alkaline earth metals
Electron Configurations and the Periodic Table • p block • Configurations end in p1 – p6 • Compose elements that make up groups 13-18 (except He) • Group 17 also called halogens (most reactive nonmetals) • Group 18 also known as noble gases • The s-block and p-block together are known as the main group elements.
Electron Configurations and the Periodic Table • d-block • Elements whose configurations end in d1 – d10 • d-block elements also known as transition elements. • Metals in the d-block tend to have higher melting points, are harder, more dense, and less reactive compared to the metals found in the s-block. • f-block • Elements whose configurations end in f1 – f14. • Composed of elements that make up lanthanide and actinide series.
Electron Configurations and the Periodic Table • When writing electron configurations using the periodic table, • the number in front of the s is the period number • the number in front of the p is the period number • the number in front of the dis one less than the period number • the number in front of the f is two less than the period number
Sample Problems Using the period table, write the electron configuration for these atoms: • chlorine (Cl) (b) barium (Ba)
Shorthand (Noble Gas) Configurations • Sometimes we are only interested with electrons in the highest energy level. • In shorthand configurations, we start with the noble gas before the element and build from there. • Bromine (Br) [Ar] 4s2 3 d10 4p5
Sample Problems Write shorthand (noble gas) configurations for these atoms: • sulfur (S) • indium (In)
Using Shorthand Configurations • Give the identity, the block, period, and group for the atom that has the following shorthand configuration [Ar] 4s2 3d10 4p3 Identity: _________ Period:_________ Block: ___________ Group:_________