Lecture 1 Flashcards
What are the characteristics of a compound different from its elements?
Sodium ( na) solid rock
Chloride ( cl) = poisonous gas
Sodium chloride = solid salt
What are some examples of naturally occurring elements?
Silver
Sulfur
Mercury
What are essential elements?
Elements that organisms need to live and reproduce
What percent of the 92 natural elements are essential elements?
20 - 25%
What are some examples of essential elements?
Carbon, hydrogen, oxygen and nitrogen (make up 96% of living matter)
Potassium, calcium, phosphorus and sulfur (the remaining 4%)
What are trace elements?
What are some examples?
Trace elements are those required by an organism in minute quantities (less than 0.01% )
Boron, chromium, cobalt, copper, iron, iodine and zinc
Given the makeup of the human body, what compound do you think accounts for the high percentage of oxygen?
Water
Is a trace element an essential element? Why?
Yes but only in small quantities
Because they can effect the body functions if they are presented in lower than the optimum quantities
In humans iron is a trace element required for the proper functioning of hemoglobin the molecule that carries oxygen in red blood cells, what might be the effects of an iron deficiency?
A person with Von deficiency will probably show fatigue and other effects of low oxygen level In the blood.
What is an atom?
An atom is the smallest unit of matter that still retains the properties of an element
What does an atom consist of?
Positive nucleus surrounded by negative electrons
What is an atom composed of?
Subatomic particles
What are the subatomic particles composed within an atom?
Neutrons ( no electrical charge)
Protons I positive charges)
Electrons (negative charges)
What does the atomic nucleus contain?
Neutrons and protons
Atomic number
The number of protons in its nucleus
Atomic mass
The total number of protons und neutrons in the nucleus of an atom
What is an atom neutral in?
Electrical charge, number of protons = number of electrons
What are isotopes?
Atoms of the same element with the same number of protons and only differ in the number of neutrons, the mass number (not the atomic number)
(Though the isotopes of an element have slightly different masses they behave identically in chemical reactions.)
radio active isotopes
Several isotopes are unstable, their nuclei decay spontaneously loosing subatomic particles und emitting energy,
Radioactive isotopes emits energy in the form of radiation
How are radioactive isotopes of iodine used?
Both the diagnosis and treatment of thyroid cancer.
How is radio active isotopes in iodine used to treat thyroid cancer?
The thyroid will normally absorb some iodine to produce iodine-containing thyroid hormones
An overactive thyroid will absorb a larger amount of the radioactive material
Electron Shells = orbitals
Electrons are found in different electron shells, each with a characteristic average distance from the nucleus and different energy levels.
The further the shell is from the nucleus, the more energy they have.
An electron can move from one shell to another
Electrons jump between energy levels by either gaming or losing energy, and the energy they release when falling back is often visible as light
Electron shells and valence shells
The farther a shell is from the nucleus the larger it is, the more electrons it can hold, and the higher the energies of those electrons
Energy levels
How many electrons can each level hold?
1st level =2
2nd level =8
3rd level = 18
4th level = 32
Valence electrodes
The chemical behavior of an atom depends mostly on the number of electrons in its outermost shell.
We call those outer electrons valence electrons and the outer most shell the valence shell
Chemical bonds
Caused by atoms with incomplete valence shells sharing valence electrons with other certain atoms.
This results in atoms staying close together, held by attractions which are known as chemical bonds.
The formation and function of molecules depend on the chemical bonding between atoms.
Covalent bonds
A covalent bond is the sharing of a pair of valence electrons by two atoms
In a covalent bond, the shared electrons count as part of each atom’s valence shell
What are the strongest chemical bonds?
Covalent bonds
What can covalent bonds form between?
Atoms of the same element or atoms of different elements
Types of covalent bonds
Single bonds - water ( shares 2 electrons)
Double bonds - Carbon dioxide ( shares 4 electrons)
Triple bonds - nitrogen ( shares 6 electrons)
Non-polar covalent bonds
In a covalent bond between two atoms of the same element, the electrons are shared equally because the 2 atoms have the same electronegativity
What is electronegativity?
The force of attraction of atoms by the electrons on a covalent bond
The more electronegative an atom is, the more strongly it puts shared electrons towards itself
Polar covalent bonds
When an atom is bonded to a more electronegative atom, the electron of the bond are not shared equally
Ionic bond
When two atoms are very unequal in their attraction, the more electronegative atom strips an electron completely away from its partner
The two resulting oppositely charged atoms (or molechles) are called Lons
What do you call a positively charged ion and a negatively charged ion?
Cation
Anion
Hydrogen bonds
Forms when a hydrogen atom covalently bonded to one electronegative atom, is attracted to another electronegative atom
What does a hydrogen bond create?
Creates a weak electrostatic attraction between the slightly positive H of one molecule and the slightly negative charge of another electronegative atom ( eg. Oxygen and nitrogen)
Van der Waals Interactions
Attractions between molecules that arise due to temporary or included dipoles
What results in temporary or included dipoles?
The movement of electrons in atoms and molecules can result in “ hot spots” of positive or negative charge.
Are electrons evenly distributed?
Not always, they may accumulate by chance in one part of a molecule or another
