Chemistry · Ch 3 — Periodic Classification of Elements
Modern Periodic Table
Modern Periodic Table
The physical and chemical properties of an element are closely tied to the arrangement of electrons in its outermost (valence) shell. Elements that share the same valence-shell configuration tend to share similar properties -- for example, every element with a single electron in an outer s-orbital behaves broadly like every other such element, which is exactly why they are grouped together as Group 1 (Table 3.6: Li, Na, K, Rb, Cs, Fr, all with a valence-shell configuration of ns1, where n increases down the group).
Extending this idea to all the elements gives the modern periodic table its familiar shape: 18 vertical columns (groups) and 7 horizontal rows (periods). Groups are numbered 1 to 18 under the IUPAC convention, which replaced the older labelling scheme of IA-VIIA, IB-VIIB and VIII. …
| Element | Atomic number | Electrons in shells (K,L,M,N,P...) | Valence shell configuration |
|---|---|---|---|
| Li | 3 | 2, 1 | 2s1 |
| Na | 11 | 2, 8, 1 | 3s1 |
| K | 19 | 2, 8, 8, 1 | 4s1 |
| Rb | 37 | 2, 8, 18, 8, 1 | 5s1 |
What this figure shows. The full 18-group, 7-period long-form periodic table with all 118 elements placed by increasing atomic number. Each cell shows the element's symbol (with atomic number and, typically, atomic mass). Groups run vertically (numbered 1-18 left to right) and periods run horizontally (numbered 1-7 top to bottom). The s-block (groups 1-2) sits at the left, the p-block (groups 13-18) at the right, the d-block (groups 3-12) in the middle, and the f-block (the lanthanides and actinides) is detached and printed as two extra r …