Lecture 1 Flashcards by Chara David

What are the characteristics of a compound different from its elements?

Sodium ( na) solid rock
Chloride ( cl) = poisonous gas
Sodium chloride = solid salt

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What are some examples of naturally occurring elements?

Silver
Sulfur
Mercury

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What are essential elements?

Elements that organisms need to live and reproduce

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What percent of the 92 natural elements are essential elements?

20 - 25%

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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%)

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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

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Given the makeup of the human body, what compound do you think accounts for the high percentage of oxygen?

Water

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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

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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.

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What is an atom?

An atom is the smallest unit of matter that still retains the properties of an element

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What does an atom consist of?

Positive nucleus surrounded by negative electrons

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What is an atom composed of?

Subatomic particles

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What are the subatomic particles composed within an atom?

Neutrons ( no electrical charge)
Protons I positive charges)
Electrons (negative charges)

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What does the atomic nucleus contain?

Neutrons and protons

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Atomic number

The number of protons in its nucleus

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Atomic mass

The total number of protons und neutrons in the nucleus of an atom

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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