The Chemistry of Living Cells

What are ATOMS? Atoms are the basic building blocks of matter that make up everyday objects. A desk, the air, even you are made up of atoms! There are 90 naturally occurring kinds of atoms. Scientists in labs have been able to make about 25 more.

Everything is composed of ATOMS!

Atoms are made of? Three basic particles: –Electrons-carry a negative charge, are outside nucleus (in a neutral atom, same # as # of protons) –Protons-carry a positive charge, are inside nucleus (in a neutral atom, same # as # of electrons) –Neutrons-carry NO charge, are inside nucleus –Ions = atoms (or molecules) with missing or extra electrons, giving it an electrical charge (+ or -)

Draw this diagram and label the parts:

Atoms Contain Energy! It takes energy to prevent the (-) electrons from crashing into the (+) protons. WHY? Electrons are organized in an electron cloud in different energy levels. The farther away from the nucleus the energy levels is, the higher the energy. The electron cloud shows the most probable location of the electrons. More to come in Chemistry!!!

Energy Levels VALENCE ELECTRONS –The electrons in the outermost energy level. –The maximum number is 8. These are the electrons involved in chemical bonding. The energy level can have less than the maximum but then it is UNSTABLE/UNHAPPY. The atom will GAIN or LOSE electrons to become stable add: (OR IT MAY SHARE!!!!) This will get more complicated in chemistry!!!)

Periodic Table Represents atoms that make up elements

Elements ELEMENTS: Pure substances that consist entirely of one type of atom; Cannot be broken down into simpler substances Elements related to living things:

How to read an element on the periodic table? Atomic # = # of protons and #electrons Atomic mass = # of protons PLUS # neutrons Protons = atomic # Electrons = same as protons/atomic # Neutrons = atomic mass – atomic #

Practice!! HydrogenCarbon

Answers! Hydrogen Atomic # = 1 Atomic mass = 1 Protons = 1 Electrons = 1 Neutrons = 0 Carbon Atomic # = 6 Atomic mass = 12 Protons = 6 Electrons = 6 Neutrons = 6 Extension: Draw these atoms above the chart!!!

Bonds and Compounds COMPOUND = a group of atoms held together by chemical bonds. Example: NaCl, H 2 O

Chemical Formulas for Compounds CHEMICAL FORMULA: Shows the number of each element in the compound  Each capital letter is a new element Subscript: (# below the symbol) tells how many atoms of that element there are –If there is not a subscript, it is considered ONE atom Coefficient: # in front of the chemical formula, tells how many of that compound there are Examples: C 6 H 12 O 6 2C 6 H 12 O 6

Types of Bonds Covalent Ionic Hydrogen

COVALENT BONDS = Occur when two atoms share a pair of electrons; called molecules, not compounds MOLECULE = a group of atoms held together by covalent bonds. Example = Water

IONIC BONDS = when one or more electrons are transferred from one atom to another (one loses electron(s), one gains electron(s)

*Sodium loses an electron-becomes a positive cation. *Chlorine gains an electron; becomes a negative anion. The attraction between the cation and anion makes the ionic bond.

HYDROGEN BOND = a weak chemical bond that forms between 2 polar molecules. POLAR MOLECULES = unequal areas of charge. Water molecules have a slight (+) charge at the hydrogen and slight (-) charge at the oxygen that causes them to attract forming hydrogen bonds.

Summary of chemical bonds Covalent: weak (melting sugar) Ionic: strong (hard to melt salt) Hydrogen bonds: weakest (individually), but strong collectively.