Biology Midterm Study Guide

Pages: 4 (754 words) Published: October 29, 2014
Biology Midterm Review

Chapter 2- The Chemical Basis of Life 1:

Atoms - The smallest functional units of matter that form all chemical substances -Cannot be further broken down into other substances by ordinary chemical or physical means -Each specific type of atom is a chemical element

Three Subatomic Particles:
-Protons – Positive (+1), found in nucleus, same number as electrons -Neutrons – Neutral (0), found in nucleus, number can vary -Electrons – Negative (-1), found in orbitals, same number as protons

Atomic Nucleus: Center of atom where protons and neutrons are confined, entire atom has no electric charge

-Areas in which the probability of finding an electron is high -“S” orbitals are spherical
-“P” orbitals are propeller or dumbbell shaped
-Each orbital can only hold 2 electrons
oAtoms with more then 2 electrons will have more then one orbital oOrbitals occupy energy shells that are associated with specific energy levels -Atoms with progressively more electrons have orbitals within electron shells -Are at greater distances from the centre of the nucleus

o1st shell is 1 spherical orbital (1s) which holds 2 electrons o2nd shell is 1 spherical orbital (2s) and 3 dumbbell-shaped orbitals (2p) •Holds 4 pairs of electrons
Valence electrons: Electrons in the outer shell
Available to combine with other atoms
Electron Energy:
An atom’s electrons:
-Vary in the amount of energy they possess
-Is defined as the capacity to cause change
Potential energy
-Is the energy that matter possesses because of its location or structure

-An electron can move from one level to another only if the energy it gains or loses is exactly equal to the difference in energy between the two levels. Arrows indicate some of the step-wise changes in potential energy that are possible

Positive particles which distinguish one element from another •Atomic number
Number of protons in an...
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