Biology Chapter 2
What are the essential elements?
Carbon, Hydrogen, Oxygen, and Nitrogen
What makes up 96% of living matter?
The essential elements
A substance consisting of two or more elements combined in a fixed ratio
Has characteristics different from those of its elements
Anything that takes up space and has mass
Substances that cannot be broken down to other substances by chemical reactions
What are organisms composed of?
What is matter made up of?
Are required by an organism in only minute quantities
What does an elements properties depend on?
The structure of its atoms
Consists of a certain kind of atom that is different from those of other elements
The smallest unit of matter that still retains the properties of an element
Atoms of each element are composed of even smaller parts called..
Relevant subatomic particles
Neutrons, Protons, Electrons
Have no electrical charge
Are positively charged
Are negatively charged
Are found in atomic nucleus
Protons and neutrons
Surround the nucleus in a cloud
Atoms of various elements differ in their number of..
The atomic number is..
The number of protons
(unique to each element)
The sum of protons plus neutrons in the nucleus of an atom
The mass number of an element
Differ in the number of neutrons and have the same amount of protons
Spontaneously give off particles and energy
Vary in the amount of energy the possess
An atoms electrons
The capacity to cause change
The energy that matter posseses because of its location or structure
Are reperesented by electon shells
Defined by its electron configuration and distribution
The chemical behavior of an atom
In the outermost, or valence shell of an atom
Determine the chemical behavior of an atom
The three-dimensional space where an electron is found 90% of the time
The sharing of a pair of valence electrons
A covalent bond
Consists of two or more atoms held together by covalent bonds
The sharing of one pair of valence electrons
A single bond
The sharing of two pairs of valence electrons
A double bond
The attraction of a particular kind of atom for the electrons in a covalent bond
The more electronegative an atom..
The more strongly it pulls shared electrons toward itself
When the atoms have similar electronegativities and share electrons equally
Nonpolar covalent bond
When the atoms have differing electronegativities and share the electrons unequally
Polar covalent bond
An attraction between anions and cations
Sometimes strip electrons away from their bonding partners
Electron transfer between two atoms creates..
Atoms with more or fewer electrons than usual
Negatively charged ions
Positively charged ions
Often called salts, which may form crystals
Forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atm
A hydrogen bond
Occur when transiently positve and negative regions of molecules attract each other
Van der Waals interactions
Reinforce the shapes of large molecules and help molecules adhere to each other
Weak chemical bonds
Is determined by the positions of its atoms valence orbitals and is usually very important to its function in the living cell
The precise shape of a molecule
Determines how biological molecules recognize and respond to one another with specificity
The making and breaking of chemical bonds
Leads to changes in the compostion of matter
Convert reactants to products
An example of a chemical reaction:
Is reached when the forward and reverse reaction rates are equal
Biology Chapter 2