Chapter 2 Basic Chemistry

Matter and Energy Matter – anything that occupies space and has mass (weight) Physical vs Chemical changes Energy – the ability to do work Kinetic • Potential Chemical • Electrical Mechanical • Radiant Law of Conservation of Energy- change forms

Composition of Matter Elements Atoms Fundamental units of matter 96% of the body is made from four elements Carbon (C) Oxygen (O) Hydrogen (H) Nitrogen (N) Atoms Building blocks of elements

Atomic Structure Inside nucleus Protons (p+) Neutrons (n0) Outside nucleus in shells /clouds / or orbitals Electrons (e-) Valence e- (outside) determine chemical rxns

Identifying Elements Atomic number Atomic mass number Equal to the number of protons that the atoms contain Atomic mass number Sum of the protons and neutrons

Atomic Weight and Isotopes Isotopes – Carbon-12 and Carbon-14 Have the same number of protons Vary in number of neutrons Atomic weight Close to mass number of most abundant isotope Atomic weight reflects natural isotope variation

Radioactivity Radioisotope Radioactivity Heavy isotope Tends to be unstable Decomposes to more stable isotope Radioactivity Process of spontaneous atomic decay Alpha, beta, gamma

Molecules and Compounds Molecule – two or more like atoms combined chemically Compound – two or more different atoms combined chemically Carbon dioxide CO2

Chemical Reactions Atoms are united by chemical bonds Atoms dissociate from other atoms when chemical bonds are broken

Electrons and Bonding Bonding involves interactions between electrons in the outer shell (valence shell) Full valence shells do not form bonds

Chemical Bonds 1. Ionic Bonds Ions - charged particles electrons transferred from one atom to another Ions - charged particles Anions are negative (Cl-) Cations are positive (Na+)

Chemical Bonds 2. Covalent Bonds Electrons are shared Single covalent bonds share one electron Double covalent bonds share two electrons

Examples of Covalent Bonds

Polarity Polar covalent bonds Non-polar covalent bonds e- shared equally No charge; neutral Non-polar covalent bonds e- shared unequally Results in positive and negative sides Have you bent water?

Carbon bonds Covalent bonds between two carbon atoms Single bonds Double bonds Triple bonds Quadruple bonds Important for organic compds

Chemical Bonds 3. Hydrogen bonds Weak chemical bonds Hydrogen is attracted to negative portion of polar molecule Provides attraction between molecules

Patterns of Chemical Reactions 1. Synthesis reaction (A+BAB) Atoms or molecules combine Energy is absorbed for bond formation Also called anabolic 2. Decomposition reaction (ABA+B) Molecule is broken down Chemical energy is released Also called catabolic

Synthesis & Decomposition Reactions

3. Exchange reaction (AB + C AC+B) single (AB+CD  AD+CB) double Involves both synthesis and decomposition reactions Switch is made between molecule parts and different molecules are made Ex. Neutralization – acid/base reaction