Unit 1 Chapter 2: Chemistry of Life Section 1: Nature of Matter Atom Smallest unit of matter that can?t be broken down by chemical means Protons, Neutrons, Electrons Electron cloud Region around nucleus that electrons can occupy at any time Stable atoms usually have no charge 1 electron for every 1 proton Elements Pure substance made of one kind of atom Differ in number of protons Ex. Carbon-12 (Carbon has 6 protons) 12-6=6 Carbon-12 has 6 neutrons Compound Substance made of joined atoms of 2 or more different elements Chemical formula identifies what is in compound and those elements? proportions Ex. NaCl 1 Sodium for every 1 Chlorine Covalent Bonds Two or more atoms share electrons to form a molecule Molecule Group of atoms held together by covalent bonds
Holt Biology Chapter 2 Section 1
Unit 1 Chapter 2: Chemistry of Life Section 1: Nature of Matter Atom Smallest unit of matter that can?t be broken down by chemical means Protons, Neutrons, Electrons Electron cloud Region around nucleus that electrons can occupy at any time Stable atoms usually have no charge 1 electron for every 1 proton Elements Pure substance made of one kind of atom Differ in number of protons Ex. Carbon-12 (Carbon has 6 protons) 12-6=6 Carbon-12 has 6 neutrons Compound Substance made of joined atoms of 2 or more different elements Chemical formula identifies what is in compound and those elements? proportions Ex. NaCl 1 Sodium for every 1 Chlorine Covalent Bonds Two or more atoms share electrons to form a molecule Molecule Group of atoms held together by covalent bonds
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