Biology Lecture 2
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Substance that cannot be broken down into other substances by ordinary chemical means.
How many naturally occuring elements?
How many are present in the human body?
92 naturally occuring elements
25 in the human body
Elements symbol for sodium
short for Natrium which is Latin
- Carbon Dioxide
What are atoms made up of?
- 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
Where are the subatomic particles found in the atom?
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.
What can make atomic weight increase?
- 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
All elements try to become stable. How many electrons are in each shell of a stable element?
1st energy shell - 2 electrons
2nd energy shell - 8 elecrtons
3rd endergy shell - 8 electrons
Three Types of Chemical Bonds
- 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
TWO ATOMS SHARE ONE OR MORE PAIRS OF OUTER SHELL ELECTRONS
THESE TWO OR MORE ATOMS FORM A MOLECULE.
example 02 and H2
What is an ion?
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.
What is a cation?
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
What is an anion?
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)
What are the three forms of matter?
Matter is anything that takes up space and has mass.
- 3 forms of matter:
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
Other elements in the human body
Other elements in the human body
required my an organism in only minute quantities
eg. iron (Fe), iodine (I), zinc (Zn)
How do you deduce the number of neutrons in an atom?
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
Emergent Properties of water that are important for life
- 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.
Forms of water
- 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
Universal Solvent of Life
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
transfer of heat
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)
hydrogen ion (H+)
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
hydroxide ion (OH-)
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)
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