Identify the four elements that make up 96% of living matter.

Oxygen, Carbon, hydrogen, nitrogen.

Trace element

Required by by an organism in only minute quantities

Ex: In vertebrates animals with backbone, the element iodine is an essential ingredient of hormones produce by the thyroid gland.

Neutron

electrically neutral

Proton

one unit of positive charge

electron

one unit of negative charged

Atomic Number

Atomic number is only the number of protons in the nucleus of the atom, giving the atom it's identity as a particular element

Mass number

Mass number is the total number of protons and neutrons in the most common isotope of an atom

Atomic Mass and weight

Mass number is an absolute -- it is the total number of protons and neutrons in an atom
Atomic weight is the ratio of the average mass of the atom relative to 1/12 of the weight of a carbon atom.

How can a atomic number and mass number of an atom can be used to determine the number of neutrons?

Subtract atomic number from mass number and you will have the number of neutrons

How to Isotopes of an element are similar. How the are different.

The two isotopes of an element have the same number of protons but different numbers of neutrons

Describe a biological application that uses radioactive isotopes.

Certain kidney disorders are diagnose by injecting small dose of radioactively-labled substance into the blood and then analyzing the tracer molecules excreted in the urine.

energy

Capacity to cause change

Potential Energy

energy that matter has because of its ability to make energy (location or structure)

Why electrons in the first electron shell have less potential energy that electrons in higher electron shells?

The frist electron shells looses energy and has the lowest potential energy. the higher electron shell gains energy and it has more potential energy.

Nonpolar covalent bonds

Sharing two atoms. The atoms share the electrons equally.
Ex: The single bond of H2 is non polar as it is the double bond of O2

polar covalent bond

one atom is more electronegative and the atoms do not share the electron equally

Ex: Bonds between oxygen and hydrogen atoms of a water molecule are quite polar.

A polar covalent bond is a chemical bond where the shared electrons spend more time closer to the nucleus of the more electronegative atom.

ionic bonds

Attraction between an anion and cation.

in an ionic bond, the electrons are completely transferred from one atom to another rather than shared.

Cation

positively charged ion.

Anion

negatively charged ion.

Why are strong covalent bonds and weak bonds essential in living organisms?

Strong covalent bonds are needed for living organisms so that organism bodies can form and hold together and not fall apart.
Water is made of weak hydrogen bonds, which make it a solvent, and water is needed for life to dissolve nutrients for ingestion or wastes for excretion, to transport important chemicals or even be used as one.

Hydrogen Bonds

from when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom. In living cells the electronegative partners are usually oxygen and nitrogen atoms.

Van der Waals interactions

are attraction between molecules that are closer together as a results of these charges

How a molecules shape can determine its biological function.

Shape is determine by position of the atoms orbital, in a covalent bond the s and p orbitals may hybridize creating specific molecule shapes. Molecules shapes is crucial in biology because it determines how biology molecules specifically recognize and respond to one another. The shape they make is called tetrahedron.

What is meant by chemical equilibrium?

When is reached when the forward and reverse reaction occurs at the same rate.

reactants

the staring molecule of a chemical reaction

products

final molecule od chemical reaction.

What is the difference between a compound and a molecule?

Chemical bond = molecule
crystalline structure or atom by itself -- not a molecule

1 A molecule consists of two more atoms, which can be the same or different types of atom, that are linked by a chemical bond. A molecule of H2 or O2 is still a molecule, but not a compound.
2. A compound is usually a molecule as well. To be a compound, it has to have two different types of atoms, such as H2O.
3. Some compounds like NaCl are not molecules because they are linked together in a crystalline structure, rather than being molecularly bonded.