Basic Chemistry

Matter and Energy Matter—anything that occupies space and has mass (weight) Matter—anything that occupies space and has mass (weight) Energy—the ability to do work Energy—the ability to do work –Chemical –Electrical –Mechanical –Radiant

Composition of Matter Elements—fundamental units of matter Elements—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 Atoms—building blocks of elements

Atomic Structure Nucleus Nucleus –Protons (p + ) –Neutrons (n 0 ) Outside of nucleus Outside of nucleus –Electrons (e - ) Figure 2.1

Atomic Structure of Smallest Atoms

Identifying Elements Atomic number—equal to the number of protons that the atom contains Atomic number—equal to the number of protons that the atom contains Atomic mass number—sum of the protons and neutrons Atomic mass number—sum of the protons and neutrons

Isotopes and Atomic Weight Isotopes Isotopes –Have the same number of protons –Vary in number of neutrons Figure 2.3

Isotopes and Atomic Weight Atomic weight Atomic weight –Close to mass number of most abundant isotope –Atomic weight reflects natural isotope variation

Radioactivity Radioisotope Radioisotope –Heavy isotope –Tends to be unstable –Decomposes to more stable isotope Radioactivity—process of spontaneous atomic decay Radioactivity—process of spontaneous atomic decay

Molecules and Compounds Molecule—two or more like atoms combined chemically Molecule—two or more like atoms combined chemically Compound—two or more different atoms combined chemically Compound—two or more different atoms combined chemically

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

Electrons and Bonding Electrons occupy energy levels called electron shells Electrons occupy energy levels called electron shells Electrons closest to the nucleus are most strongly attracted Electrons closest to the nucleus are most strongly attracted Each shell has distinct properties Each shell has distinct properties –The number of electrons has an upper limit –Shells closest to the nucleus fill first

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

Inert Elements Atoms are stable (inert) when the outermost shell is complete Atoms are stable (inert) when the outermost shell is complete How to fill the atom’s shells How to fill the atom’s shells –Shell 1 can hold a maximum of 2 electrons –Shell 2 can hold a maximum of 8 electrons –Shell 3 can hold a maximum of 18 electrons

Inert Elements Atoms will gain, lose, or share electrons to complete their outermost orbitals and reach a stable state Atoms will gain, lose, or share electrons to complete their outermost orbitals and reach a stable state Rule of eights Rule of eights –Atoms are considered stable when their outermost orbital has 8 electrons –The exception to this rule of eights is Shell 1, which can only hold 2 electrons

Inert Elements Figure 2.5a

Reactive Elements Valence shells are not full and are unstable Valence shells are not full and are unstable Tend to gain, lose, or share electrons Tend to gain, lose, or share electrons –Allow for bond formation, which produces stable valence

Chemical Bonds Ionic bonds Ionic bonds –Form when electrons are completely transferred from one atom to another Ions Ions –Charged particles  Anions are negative  Cations are positive  Either donate or accept electrons

Ionic Bonds Figure 2.6 +– Sodium atom (Na) (11p + ; 12n 0 ; 11e – ) Chlorine atom (Cl) (17p + ; 18n 0 ; 17e – ) Sodium ion (Na + )Chloride ion (Cl – ) Sodium chloride (NaCl) ClNaCl Na

Chemical Bonds Covalent bonds Covalent bonds –Atoms become stable through shared electrons –Single covalent bonds share one pair of electrons –Double covalent bonds share two pairs of electrons

Examples of Covalent Bonds Figure 2.7a

Examples of Covalent Bonds Figure 2.7b

Examples of Covalent Bonds Figure 2.7c

Polarity Covalently bonded molecules Covalently bonded molecules –Some are non- polar  Electrically neutral as a molecule –Some are polar  Have a positive and negative side Figure 2.8

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

Hydrogen Bonds Figure 2.9

Patterns of Chemical Reactions Synthesis reaction (A + B  AB) Synthesis reaction (A + B  AB) –Atoms or molecules combine –Energy is absorbed for bond formation Decomposition reaction (AB  A + B) Decomposition reaction (AB  A + B) –Molecule is broken down –Chemical energy is released

Synthesis and Decomposition Reactions Figure 2.10a

Synthesis and Decomposition Reactions Figure 2.10b

Patterns of Chemical Reactions Exchange reaction (AB + C  AC + B) Exchange reaction (AB + C  AC + B) –Involves both synthesis and decomposition reactions –Switch is made between molecule parts and different molecules are made

Patterns of Chemical Reactions Figure 2.10c