CHEM 1211 Lecture Notes - Lecture 1: Significant Figures, Atomic Number, Atom
Document Summary
Chem, 1211, chapter 1: **matter**: matter is anything that has mass and occupies space. It can be classified into three main states: solid, liquid, and gas: **elements and compounds**: elements are the simplest forms of matter that cannot be broken down into simpler substances by ordinary chemical means. Compounds are substances composed of two or more elements in fixed proportions: **atoms**: atoms are the smallest units of an element that retain the properties of that element. Atoms consist of a nucleus (made up of protons and neutrons) and surrounding electrons: **atomic structure**: the atomic number (z) is the number of protons in the nucleus of an atom, and it defines the element. The mass number (a) is the sum of protons and neutrons in the nucleus. Elements in the same group (vertical column) have similar chemical properties, while periods (horizontal rows) indicate repeating trends in properties: **chemical reactions**: chemical reactions involve the rearrangement of atoms to form new substances.
