Biology Lecture 2

Substance that cannot be broken down into other substances by ordinary chemical means.

92 naturally occuring elements

25 in the human body

Na

short for Natrium which is Latin

• Oxygen
• Hydrogen
• Carbon
• Carbon Dioxide
• Nitrogen

• smallest unit of matter that still retains the properties of an element.
• Made up of subatomic particles:

• Electrons - (-) negative charge
• Protons - (+) positive charge
• Neutrons - no charge

Protons and neutorns are in the nucleus

Electrons are outside the nucleus in the energy shell (also called the electron shell)

Weight and mass are basically similar

The atomic weight is determined by the protons and neutrons (subatomic particles in the nucleus)

Weight measured in daltons (John Dalton - 1800) or amu (atomic mass units). Protons and neutrons have mass close to 1 dalton.

The number of protons found in the nucleus of an atom. Each number is unique to that element. Eg every Hydrogen atom will have 1 proton in its nucleus.

Normally, an atom is neutral in electrical charge - must be balanced in the number of protons and electrons. Atomic number tells the number of protons and electrons in an electrically neutral atom.

Atoms of a given element have the same number of protons, but some have more neutrons and therefore have greater mass

Although the isotopes have different masses they behave identically in chemical reactions.

ex. Carbon had 6 protons making it number 6 on the periodic table. 14C has those 6 protons and 8 neutons (6+8=14). Isotopes make atomic weight heavier.

• Isotopes make atomic weight heavier.
• Carbon had 6 protons making it number 6 on the
• periodic table. 14C (Carbon-14) has those 6 protons and 8 neutons (6+8=14).

DETERMINE CHEMICAL BONDS.

PHYSICAL AND CHEMICAL PROPERTIES ARE DETERMINED BY THEM

1st energy shell - 2 electrons

2nd energy shell - 8 elecrtons

3rd endergy shell - 8 electrons

IONIC

COVALENT

HYDROGEN

• SALTS One atom donates an electron to another. Any two ions of opposite charge can form an ionic bond.
• Sodium Chloride is blanced and stable due to ionic bonds
• 

STRONG BOND

TWO ATOMS SHARE ONE OR MORE PAIRS OF OUTER SHELL ELECTRONS

THESE TWO OR MORE ATOMS FORM A MOLECULE.

example 0₂ and H₂

A charged atom is called an ion

• An atom is charged when number of protons and electrons are not the same.
• Positive when there are more protons than electrons - cation
• Negative when there are more electrons than protons - anion

A negatively and positively charged ion will attract to one another forming an ionic bond.

a cation is a positively charged ion.

When sodium (Atomic number 11) give an elecrton to chloride it now has 11 protons and 10 electrons. It is a +1 charged ion called a cation

A negatively charged ion

When chloride (atomic number 17) gets an electron form sodium it has 17 protons and 18 electrons making it a -1 negatively charged particle called an anion.

Weak bond - important to biological life

Forms whenever a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom

Unequal sharing results in Polar Molecules (water the most important one)

Matter is anything that takes up space and has mass.

• 3 forms of matter:
• solid
• liquid
• gas

Substance consisting of two or more different elements combined in a fixed ratio.

• Has characteristics that are different that those of its elements
• sodium - metal
• chloride - poisonous gas
• sodium chloride - salt

• Calcium
• Phosphorus
• Potassium
• Sulfur

• Sodium
• Chlorine
• Magnesium

required my an organism in only minute quantities

eg. iron (Fe), iodine (I), zinc (Zn)

atomic mass number (protons and neutrons combined) minus atomic number (number of protons). Remember that protons and neutrons basically weigh 1 dalton so the difference is the number of neutrons

isotopes in which the nucleus decays spontaneously, giving off particles and energy. When the decay leads to a change in the number of protons the atom transforms into another element. (carbon decays to form nitrogen).

These are important to us in medicine C-14 or Carbon 14 (6 protons +8 neutons)

Energy is the capacity to cause change

• Potential energy is the energy that matter possesses because of its location or structure.
• (the further an electron is from the nucleus the more potential energy)

Valence electrons are the ones in the outermost shell (the valence shell). They determine the behavior of the atom....if the valence shell is full the atom will be inert (non-reactive). If the valence shell is not full the atom will be chemically reactive at it looks to become stable.

do not share electrons equally - tug of war

• 1 .cohesion - ability to stick to each other
• adhesion - ability to cling to other substances
• surface tension

• 2. moderation of temperature
• 3. Exists as liquid, solid and gas
• 3. versatility as solvent

• water absorbs heat from the air when it is warmer and releases heat when the air is cooler
• heat is a form of energy (kinetic energy due to motion of atoms/ molecules)
• temperature is a measure of heat intensity

RELATED TO COHESION – DIFFICULTY OF BREAKING OR STRETCHING THE SURFACE OF A LIQUID.

• EXISTS AS LIQUID, SOLID, AND GAS.
• WATER AS LIQUID MORE DENSE THAN SOLID (ICE). ( WHY ICE FLOATS). more space between H and O as it freezes.
• ICE ACTS AS INSULATION

Water - Solvent - dissolves many compounds

something to be dissolved

liquid which dissolves a solute (dissolving agent)

two or more items in an equal ration (mixture)

any solution in which water is the solvent

solute suspended in water - not in complete solution

stable suspension of fine particles in a liquid (they are hydrophilic but do not dissolve)

energy of motion

• water freezes at 0°C
• water boils at 100°C
• human body temp 37°C

heat is transfered as kinetic energy from a warmer object to a colder object until the two are the same temperature

any substance that has an affinity to water

does not have to dissolve -eg cotton

substances that repel water (usually nonionic or nonpolar - they cant form hydrogen bonds)

a hydrogen atom participating in a hydrogen bond shifts from one molecule to the other. It leaves it electron behind and it just a single proton with a charge of +1

the water molecule that lost a proton when a hydrogen molecule left and left its electron behind (has a charge of -1)

substance that increases the hydrogen ion concentration of a solution

substance that reduces the hydrogen ion concentration of a solution

substances that minimize changes in the concentrations of H⁺ and OH^-

rain, snow, or fog, with a pH lower than 5.2 (normal rain pH is 5.6)

• caused by burning of fossil fuels - oil, gas, coal - carbon sources that are dead
• burning of fossil fuels causes sulfer oxides and nitrous oxides (they react with the water in the air to form acids)