Chemistry of Life

The basics of Chemistry

Matter is recycled and rearranged for living organisms

• Living matter is made up of different substances.

• Example of substances: pure CO2, glucose, pure salt, H2O…..

CO2

glucose

Atoms - Smallest unit of an element (with properties of that element)

• Nucleus - dense center containing:– Protons - positively charged

particles– Neutrons - particles with no

charge

• Electrons (e-) - small, negatively charged particles that orbit nucleus in clouds or shells (2, 8, 8)

– Valence e- - found in outermost energy level

How many total e-? How many valence e-? What element?

A=P=E M=A+N

Atomic number = Proton number = Electron number

Mass = Atomic Number +Neutrons

Click on image to play video.

Chapter 02A.mpg

• How would an element’s identity change if you took away or added protons?

Check for Understanding

The 17 essential elements in plants (autotrophs)…

CHOPKINS Ca Fe Mg B Mn Cu Zn Mo Cl

Carbon, Hydrogen, Oxygen, Phosphorous, Potassium, Iodine, Nitrogen, Sulfur, Calcium, Iron, Magnesium, Boron, Manganese, Copper, Zinc, Molybdenum, Chlorine

C HOPKINS Café Managed by my cousin Mo Cline

• 96% of living matter: C, H , O, and N

• 4% of living matter: Ca, K, P, S, Na, Cl, Mg, Fe, and trace elements

Hypothesize as to why these elements are near the top of the periodic table. (answer in the left margin)

Check for Understanding

Atoms, Molecules and Compounds

Molecules and Compounds• Molecule - 2 or

more elements joined together by chemical bonds

• smallest unit of a compound

Check for Understanding • What is the name of the

compound in the bottle?• What is the molecular

formula?• What is the structural

formula?• How many molecules of

the substance are in the bottle?

• How would you calculate this?

Chemical reactions

6CO2 + 6H2O C6H12O6 + 6O2

• Lead to changes in substance or matter.

• Occurs when electrons are transferred between two atoms (lost, gained or shared)

Octet Rule• The octet rule is a chemical

rule that states that atoms with atomic number <20 tend to combine in such a way that they each have eight electrons in their valence shells.

• 1st Shell holds up to 2 electrons max

• 2nd Shell holds up to 8 electrons

• 3rd Shell holds up to 8 electrons as well

• An Oxygen atom diagram

Practice

• Al• Mg• S• Ne• N

• Draw the atoms for the elements listed at the left and show the protons, neutrons and electrons. Under the drawing write a sentence telling me how many valence electrons there are.

Drawing Atoms• As scientists, we want to be

efficient

• Instead of drawing all of the electron shells, we only need to draw the valence electrons

• A Lewis Dot diagram will make drawing molecules and compounds easier

Lewis Dot Diagrams

• The inner shells are not involved in bonding

• Carbon is in group 14, so that means 4 valence electrons

• We often write the element symbol and only the valence electrons

You try…What does the Lewis dot diagram look like for Oxygen?

What does the Lewis dot diagram look like for Sodium?

Hydrogen?

How about Lithium?

Why are they all the same?

NaH

Li

Chapter 02B.mpg

Ions = electrically charged matter

• Ions form when electrons are lost or gained.• Ionic bonds form when a positive ion is attracted

to a negative ion.

Making Salt…Lewis dot style

(Ionic bond) positive Na+ attracted to negative Cl -

Click on image to play video.

Chapter 02C.mpg

Covalent bond = two

atoms sharing electrons

• “Strong” • Relatively stable• Hydrogen, oxygen,

and nitrogen can readily form covalent bonds with carbon.

Hydrogen Bonding• Weak bonds between

a hydrogen of one molecule to an adjacent negative molecule

• Ex: attraction between water molecules.

Mixtures

Physical combinations of substances

• There are several types of mixtures:• solutions • suspensions • Colloids, or colloidal dispersions

Mixtures

Air = solution

Physical combinations of substances

Cytoplasm = colloid

Blood = suspensionJello = colloid

Kool-Aid= solution

Name 3 solutions found in every day life.Can you think of a suspension?How about a colloidal dispersion?

Check for Understanding

Exit Ticket• Put your FULL NAME, Date and Period on

the BACK side.• Divide the ½ sheet provided into 3rds.

• In the first box, diagram an atom of Hydrogen and show the protons, neutrons and electrons including the valence electrons

• In the second box, diagram an atom of Carbon and show the protons, neutrons and electrons including the valence electrons

• In the third box, diagram an atom of Oxygen and show the protons, neutrons and electrons including the valence electrons