Chemistry What is an atom? An atom is the smallest unit of an element, that has

all the chemical and physical characteristics of the element. All matter is composed of elements, all elements are composed of atoms.

Atoms are composed of the following particles: Nucleus

Proton – positive charge Neutron – neutral charge

Electrons – have a negative charge

ElementsWhat makes one type of atom different

from another type of atom?Atoms of different types are called

elements.Atoms of different elements have

different numbers of protons (and electrons).

The Periodic Table of Elements

47

AgSilver

107.868

How many neutrons does silver have in it’s nucleus?

Bohr Models Electrons are arranged around the nucleus in

specific energy levels. We can draw a diagram to show how

electrons are arranged around the nucleus. Try these: Hydrogen, Beryllium, Carbon, Oxygen,

Nitrogen, Neon, Chlorine, Aluminum, Sodium (Do activity on first 18 elements.)

Put the symbol in the box, the name, and the Bohr Model

Electrons Have a negative charge (e-) Travel in energy levels, which contain orbitals, around the

nucleus The first “energy level”, holds 2 electrons The 2nd and 3rd energy levels can hold up to 8 electrons

each When an electron energy level is full, the next electrons

fill a new higher energy level The number of electrons = number of protons in a

neutral atom Electrons can be lost, gained, or shared when an atom

bonds with another atom

The Periodic Table of Elements It is organized! Columns on the table are called groups Group IA – have 1 electron in outer energy level These

are soft, highly reactive metals like sodium and potassium. They loose electrons and become more positive.

Group IIA – have 2 electrons in outer energy level, they are harder, metals like calcium and magnesium. They loose electrons and become more positive.

Oxygen, chlorine, in Group VIIB, are on the right side of table – their energy levels are not full. They gain electrons and become more negative. They are nonmetals.

Why do we care about the structure of

different atoms? It helps us understand how they interact

with each other to form BONDS IONIC BONDSCOVALENT BONDSHYDROGEN BONDS

Ionic BondsEx. NaCl (table salt)

Ionic Bond – forms because of a strong attraction between oppositely charged ions.

Covalent Bond Ex. Water (H20)

Covalent Bond – A bond between two atoms formed because of sharing of electrons.

HydrogenOxygen

Polar versus nonpolar molecules

If a molecule has a positive end and a negative end = POLAR molecule

Molecules without positive and negative ends = NONPOLAR molecule

Example – WATER is POLAR

ASPECTS OF WATER MOLECULE AND IT’S POLARITY The arrangement or geometry of the atoms in

some molecules is such that one end of the molecule has a positive electrical charge and the other side has a negative charge. If this is the case, the molecule is called a polar molecule, meaning that it has electrical poles. Otherwise, it is called a non-polar molecule. Whether molecules are polar or non-polar determines if they will mix to form a solution or that they don't mix well together

Chemical bonding is the result of either an atom sharing one or more outer orbit electrons with another atom or an atom taking outer orbit electrons from the atom with which it is bonding. Normally, an atom has an even distribution of electrons in the orbits or shells, but if more end up on one side that the other in a molecule, there can be a resulting electrical field in that area.

Water is a polar molecule in that the way the atoms bind in the molecule are such that there are excess electrons on the Oxygen side and

Non-polarA non-polar molecule is one that the

electrons are distributed more symmetrically and thus does not have an abundance of charges at the opposite sides. The charges all cancel out each other.

SolutionsWhen water dissolves a substance, the

liquid is a SOLUTIONWhy?NaClNa+, Cl-Na+ is attracted to?Cl- is attracted to?

Water is important!

H20 can break down into ions

H20 H+ + OH-

H+ + OH-

H+ + OH- ions are very reactive in nature

pH When some compounds dissolve in water,

ions are produced Ex. HCl (hydrochloric acid) HCl H+ + Cl-

Acids – adds H+ ions to a solution Ex. NaOH NaOH Na+ + OH-

Base – adds OH- ions to a solution

pH A measure of the amount of H+ ions or

OH- ions

pH Scale

The Compounds of Life (2-2)Organic Inorganic

Carbohydrates

Lipids

Proteins

Nucleic Acids

Chemical Reactions & Enzymes (2-3)

Enzymes

Tryptophan – mirror image molecules