Post on 26-Dec-2015
What is life made of?
Organisms are composed of __________: anything that takes up space or has mass
___________: a substance that cannot be broken down by chemical reactions
___________: substance consisting of two or more elements in a fixed ratio
Essential Elements for Life
Life requires about 25 elements4 of those make up 96% of living matter
_______________________________________________________
Trace Elements are those that are required in only minute quantities-ex. Iron, iodine
What are elements made of?
_________: smallest unit of matter that still retains the properties of an element
___________________: Protons (+), Neutrons (0), Electrons (-)
Protons and Neutrons have a mass of 1 dalton. Electrons have no mass
Atomic Number and Mass
___________________: # of protons_______________: sum of protons +
neutrons__________________: different forms of
an element (same # of protons, more neutrons)-ex. Carbon-12 (99%), Carbon-13 (1%), Carbon-14 (<1%)
Isotopes
C-12 and C-13 are stable. C-14 is unstable, and radioactive. Radioactive Isotope: atom that will
decay giving off particles and energy.
Carbon-14 will decay into NitrogenRadioisotopes are useful in science
and medicine
Electrons and Energy
An atom’s electrons vary in the amount of energy they possess.
____________: the ability to do work._______________: energy that matter
stores because of its position or location
Electrons have potential energy because of their position in relation to the nucleus.
(a) A ball bouncing down a flight of stairs provides an analogy for energy levels of electrons
Third shell (highest energylevel)
Second shell (higherenergy level)
Energyabsorbed
First shell (lowest energylevel)
Atomicnucleus
Energylost
Potential Energy
Electron Shells
The different states of potential energy that electrons have in an atom are called energy levels or electron shells.- the first shell has the lowest energy. The second shell has more than the first, etc.
__________________: those in the outermost shell
Electrons and Chemical Properties
Hydrogen
1H
Lithium
3LiBeryllium
4BeBoron
5BCarbon
6CNitrogen
7NOxygen
8O
Fluorine
9FNeon
10Ne
Helium
2HeAtomic number
Element symbol
Electron-distributiondiagram
Atomic mass
2He
4.00Firstshell
Secondshell
Thirdshell
Sodium
11NaMagnesium
12Mg
Aluminum
13AlSilicon
14SiPhosphorus
15PSulfur
16S
Chlorine
17ClArgon
18Ar
Atoms will bond with others to gain stability (fill valence shell)
________________: sharing of a pair of valence e- by two atoms-ex. Hydrogen atoms will share their electrons. They become H-H
Chemical Bonds
Types of Covalent Bonds
__________________: the attraction of an atom for the electrons of a covalent bond
____________________: when the electrons are shared equally
____________: when one atom is bonded to a more electronegative atom
Unequal sharing of electrons
_________: a charged atom formed when two atoms are so unequal in their attraction for electrons that one atom will strip the electrons from its partner
cation has a positive charge, anion has a negative charge (ca+ion; a negative ion)
_________: bond formed when cations and anions attract each other
Compounds formed by ionic bonds are salts
Ionic Bonding
Na Cl Na Cl
NaSodium atom Chlorine atom
Cl Na+
Sodium ion(a cation)
Cl–Chloride ion
(an anion)
Sodium chloride (NaCl)
The advantage of weak bonding is that the contact can be brief
_______________: H is covalently bonded to an electronegative atom and attracted to another electronegative atom.-ex. Water and ammonia
Weak bonding
Nonpolar molecules may have positively and negatively charged regions at any moment
_______________: enables nonpolar molecules to attract each other
May form between regions of the same protein help form shape
Weak bonding
Molecular Shape
Molecules have characteristic shape and size
Shape determines how molecules recognize and respond to one another
Ex: opium and endorphins
Forming and Breaking Bonds
________________: making and breaking of chemical bonds.- starting material is reactants- ending material is products
All reactions are reversible
Forward and Reverse Reactions
__________________: point at which reactions offset one another.
No net effect on concentrationAffected by concentration of
reactants or products