key term - Periodic law

Definition

The periodic law states that the properties of elements are a periodic function of their atomic numbers. When elements are arranged by increasing atomic number, their chemical and physical properties show a repeating pattern.

5 Must Know Facts For Your Next Test

1. The periodic law is the foundation for the structure of the modern periodic table.
2. Elements in the same group (column) have similar chemical and physical properties due to having the same number of valence electrons.
3. Periods (rows) on the periodic table represent elements with increasing atomic numbers and show patterns in electron configuration.
4. Periodic trends such as electronegativity, ionization energy, and atomic radius can be explained using the periodic law.
5. Mendeleev's early version of the periodic table was organized by atomic mass, but the modern table uses atomic number due to Moseley's work.

Review Questions

Related terms

Atomic Number:

The number of protons in an atom's nucleus, which determines its place on the periodic table.

Valence Electrons:

Electrons in an atom's outermost shell that determine its chemical reactivity.

Electronegativity:

A measure of an atom's ability to attract and bond with electrons; it generally increases across a period and decreases down a group.