The Chemistry of LifeChapter 2

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The Chemistry of Life

• Matter- anything that takes up space and

has mass- everything around us

• Element- Substance that cannot be

broken down to other substances by

chemical reactions.

• 92 naturally occurring

Periodic Table of Elements

• Compound- Substance of two or more

different elements combined in a fixed

ratio.

-IE- NaCl or Steel

• Essential Elements

Carbon, oxygen, nitrogen, hydrogen

compose 96% of living matter.

• Phosphorus, sulfur, potassium, calcium

and trace elements compose the

remaining 4%.

• Trace elements still necessary for life.

Trace Elements are important!

• Atom- smallest unit of matter that still

retains the properties of the element.

• Proton- positive, circa 1 Dalton *atomic

mass unit (amu), located in nucleus

• Neutron- neutral, circa 1 Dalton,

located in nucleus

• Electron- negative, circa 1/2000 of

a Dalton, orbits the nucleus

Subatomic particles-

• Atomic number: number of protons

– if a neutral atom, then proton # = electron #

• Mass number (atomic mass):

Protons + neutrons.

Mass number will be greater (or equal to, in

the case of hydrogen) than atomic number.

How many protons does this element have?

tschwartz

Atomic Number

Atomic Mass (p + n)

Let’s practice!

• Look up on the periodic table and draw

atom

• Nitrogen

• Sulfur

Q.Q. 10/18/18

• Get your notebooks!

• Look up on the periodic table and draw

Carbon

The “A” TEAM

CH. 12 & 13 TEST

❖David Anguelov

❖Rohan Benda

❖Mia Crossen

❖Belen Hernandez

❖Emily Lindley

❖Noah Rivera

Test Average: 81%

GREAT WORK! (*without extra credit question!)

• Isotope- Some elements have a differing number of neutrons. SAME chemical properties.

IE- Carbon. Exists in three different isotopes.

C-12 (99% in nature)

C-13 (almost 1%)

C-14 (miniscule amount found in nature).

C-14 is a radioisotope- nucleus decays spontaneously causing radiation.

Isotopes

Used as a “tracer” (substance used to track the flow of C in an organism)*helps determine ages of fossils

Iodine-131

• Radioactive Isotope

used to detect and

treat

hyperthyroidism and

some thyroid

cancers

• Half life to 8 days

• Energy levels of electrons- Energy is

defined as the capacity to cause change.

• Electron energy level closest to nucleus is

at lowest energy level.

• Electron energy levels increase in energy

as we move away from the nucleus.

Electrons

2, 8, 8!

* Valence e- important for atom interactions & bonding

• Valence electrons are the electrons in the

outermost shell.

– Non-reactive if this shell is full (noble

gases) *INERT; “happy”

• Orbitals:

– First shell can hold 2 electrons (1s)

– Second shell can hold 8 electrons (2s and

three 2p’s). Cannot have more than 2

electrons per orbital.Animations of valence

electrons

How many valence electrons does oxygen have?

6

Covalent Bonding

• Covalent Bonding- sharing of valence electrons. Some of the strongest bonds found in living matter.

• H-H is a single covalent bond, each H is sharing its one electron (structural formula). – H2 (molecular formula)

• Bonding capacity is based on how many electrons are needed in valence shell, and an atoms “valence” = the number of unpaired electrons in the outermost shell.

Covalent Bonding

Electronegativity

• Electronegativity- attraction of a

particular atom to the electrons shared in

a covalent bond.

• More electronegative atoms pull harder

on the electrons.

– *more greedy and becomes an “unequal

share”

Polar and non-polar COVALENT bonds

Non-polar covalent bonds

• When electrons are shared equally

between two atoms of the same type

(IE- Cl-Cl) then it is a non-polar covalent

bond.

*No pull!

Polar covalent bond

• When the electrons are NOT shared

equally it is considered a polar covalent

bond.

Electronegativity and oxygen

• Oxygen is the *2nd

most electronegative of

all 92 elements

(commonly found in an

organism).

• Where ever the

electrons are being

pulled closest to will

have a slight negative

charge (notated as δ-).

2nd Quarter!

Q.Q. 10/22/18The atomic number of Sulfur is 16. Sulfur combines with

hydrogen by covalent bonding to form a compound,

hydrogen sulfide. Based on the # of valence e- in a sulfur

atom, predict the molecular formula of the compound.

a) HS

b) HS2

c) H2S

d) H3S2

e) H4S

2nd Quarter!

Q.Q. 10/22/18The atomic number of Sulfur is 16. Sulfur combines with

hydrogen by covalent bonding to form a compound,

hydrogen sulfide. Based on the # of valence e- in a sulfur

atom, predict the molecular formula of the compound.

a) HS

b) HS2

c) H2S

d) H3S2

e) H4S

Polarity of Water Animation

Ionic Bonding

• Ionic bonding- The two atoms are so

unequal in their attraction to the valence

electrons that the stronger of the two strips

the electron away from the other atom.

*completely removes; no sharing!

IE- Sodium (11 electrons, single electron in

valence) and chlorine (17 electrons, 7 electrons

in valence). Chlorine strips the single electron

away from the sodium, fulfilling the octet in the

valence shells of both.

Ionic Bonding

Ionic Bonding

• Because of this donation, the sodium is now

positive (has 11 protons, 10 electron) and is

called a cation.

• Chlorine is now negative (17 protons and 18

electrons) and is called an anion.

• Cations and anions attract forming this ionic

bond. These bonds form salts.

Video of

formation

reaction

Antioxidants

Hydrogen Bonds

• Weak bonds- Some of the most important

bonds in living matter. Reversible

– Hydrogen bonds- H atom that is covalently

bonded to an electronegative atom is

attracted to another electronegative atom

(usually O or N in living matter).

Hydrogen Bond

Van der Waals forces

• Weak bonds

• Van der Waals forces- “hot spots” of

positive and negative charges because of

random electron movement (weak bond,

but strong enough to hold a gecko on a

wall) – TED Ed- How geckos defy gravity

Molecular shape and function

• When two matching atoms bond it will be a

linear molecule.

• Larger molecules are very complicated

and their shape is CRUCIAL in

recognition in biological systems.

Molecular shape and function

Chemical reactions

• Chemical reactions- Making and breaking

bonds.

• Reactants Product(s)

• We cannot create or destroy matter, only

rearrange it.

Photosynthesis-

6CO2 + 6H2O C6H12O6 + 6O2

Important chemical reactions

• Some reactions are reversible, some are not (said to have gone “to completion”).

• If we increase the concentration of reactants then we will speed up the reaction.

• Chemical equilibrium-Forward and reverse reactions balance each other out and there is no net effect on the concentrations of the reactants or products.

End of Chapter Concept Map

• Construct on separate paper

• Written description of relationships

Due on Tues. 10/23!

Turn in before Quiz!