Biology 1408 Ch. 2-4 Exam Essay

Submitted By Elizabeth-Keeler
Words: 4280
Pages: 18

Biology 1408 EXAM I REVIEW

I have included topics that you should be familiar with for the exam. You must be able to answer why or how different processes occur, not just what they are.

Know the differences among molecules, elements, matter
A molecule is the smallest part of a compound retaining its properties.
Elements a substance that cannot be broken down by chemical means into simpler substances with different properties.
1) All matter consists of elements.
2) Six elements are basic to life: carbon (C), hydrogen (H), oxygen (O), phosphorous (P), nitrogen (N), and sulfur (S).
Matter refers to anything that takes up space & has mass.
1) Matter exists in three distinct states: solid, liquid, and gas.
How are neutral elements and isotopes different?
Neutral Elements is an element of the zero group of the periodic system comprising the rare gases
1) Examples: He, Ne, Ar, Kr, Xe, Rn.
Isotopes are atoms of a single element that differ in their number of neutrons.
1) Isotopes have the same number of protons but have different masses. Ex.: 126C is a carbon atom with 6 neutrons and 6 protons. Ex.: 136C is a carbon atom with 7 neutrons and 6 protons.
2) Unstable isotopes break down into stable atoms with lower masses.
3) Unstable isotopes release radiation known as radiant energy.
4) These unstable isotopes are known as radioactive isotopes.
How do protons, neutron, electrons contribute to the properties of an element?
Are the three best-known subatomic particles – which are particles that are less complex then an atom but are components of an atom.
Protons are found in the nucleus of the atom.
Neutrons are found in the nucleus of the atom.
Electrons move about the atom & are located in the electron shell that circle the nucleus.
What is the difference between Atomic Mass and Atomic Number?
Atomic Number represents the number of protons found with an atom.
1) All atoms of an element have the same atomic number.
2) Carbon (C) has the atomic number 6 = 6 protons.
3) The atomic number also indicates the number of electrons when the atom is electrically neutral (has no charge): Carbon = 6 electrons.
4) The atomic number is written as a subscript to the atomic symbol
Atomic mass is the sum of protons and neutrons in an atom.
1) The atomic mass is unique for atoms of each element.
2) Electrons do not contribute to the atomic mass.
3) The term mass is more accurate than weight b/c mass always stays constant & weight is dependent on gravity (which changes in space).
4) The atomic mass is written as a superscript to the left of the atomic symbol.
What are the charges on protons? Neutrons? Electrons?
Protons are positively charged.
Neutrons are uncharged.
Electrons are negatively charged.
Be familiar with the Periodic Table. What do the columns and rows indicate about the elements?
Horizontal rows (periods) indicates how many shells are present.
Vertical columns (groups) indicate the number of electrons in the outer shell.
1) Ex.: Carbon (C): 2nd period, 4th group indicates, 2 shells & 6 electrons.
What is the Octet Rule? What does it mean?
The octet rule states that an atoms tend to react to achieve eight electrons in the outer shell (the most stable #) (or two electrons).
1) Atoms with incomplete shells react with other atoms resulting in full shells.
2) Electrons can be given up, shared, or accepted in order to fill a shell.
3) The number of electrons in an atom’s outer shell (valence shell) determines how it will react.
How are ionic and covalent bonds different?
Ionic bonds occur when electrons are transferred and hold together ionic compounds via charge attraction.
1) Occurs when particles called ions are held tighter by the attraction between positive and negative ions.
A covalent bond is the result to two atoms sharing electrons to fill shells.
1) A covalent bound can be nonpolar or polar.
2) Ex.: Hydrogen with one electron shares