1. Unit 2 Vocabulary
Atomic number – the number of protons in the nucleus of an atom; used to determine an element's position in the Periodic Table
Chemical property – a characteristic of a substance that describes how it combines with other substances to form new ones
Groups (families) – the vertical columns on the Periodic Table
Periods – the horizontal rows on the Periodic Table
Periodic Table –a conceptual model in which the elements are organized according to their properties; often displayed as a chart
Periodic trend – a regular variation of certain characteristics of elements to increase or decrease along a period (row) or group (column) of the Periodic Table of elements
Physical property – property of matter that can be observed without changing the composition or identity of the matter
Reactivity – tendency of a substance to undergo chemical changes in a system
Valence electrons – electron(s) located in outer energy level (electron shell)