the chemical level of organization atoms atomic structure electron shells, losing/gaining electrons...
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The Chemical Level of Organization
Atoms• Atomic Structure• Electron Shells, losing/gaining electrons• Ions
Molecules, their formation through bonds• Chemical Bonds (how, why, and types)
Macromolecules• 4 major macromolecules
Elements & Atoms
ElementsDifferent kinds of matter (material) that have distinct (chemical) properties
Examples:
• gold• carbon• hydrogen• sodium• nitrogen• calcium• oxygen
many different object/pictures
5 basic shapes
Atoms
Smallest unit/piece of an element (matter) that still has the properties of that element.
The structure and components of an atom
--Neutral
--positive
--negative
Electron
Neutron
ProtonElectron Shell (orbital)
NucleusElectron Shell (orbital)
2p, 2e, Helium 4p, 4e, Beryllium3p, 3e, Lithium
Different elements are made of atoms with different numbers of protons and electrons—that is why each element has its own unique set of properties
Element Number of protons
Number of electrons
% of Body by Weight
Hydrogen 1 1 9.5
Carbon 6 6 18.5
Nitrogen 7 7 3.3
Oxygen 8 8 65.0
Sodium 11 11 0.2
Sulfur 16 16 0.3
Chlorine 17 17 0.2
Valence Shellsoutermost shell of atom = valance shell
• Atoms are most stable when the outer shell is filled, or emptied.
Valance shells
Electron shells of common elementsValance in red
1st shell 2nd shell 3rd shell 4th shell
Hydrogen 1
Carbon 2 4
Nitrogen 2 5
Oxygen 2 6
Sodium 2 8 1
Chlorine 2 8 7
Potassium 2 8 8 1
calcium 2 8 8 2
Behavior of atoms and outer electron shells
Atoms “want” to have completely emptied or completely filled outer electron shells.
Atoms will gain, lose, or share electrons to fill or empty their outer shells.• This is the basis for chemical bonds and the
formation of ions
electron shell = orbital = valence shell = regions that hold electrons
Formation of ions
Gaining or Losing Electrons
Gaining ElectronsIf the outer shell is almost full, gaining electrons is likely to happen
Losing ElectronsIf the outer shell is almost empty, losing electrons is likely to happen
Note that both of these events will result in the creation of an ion.
1- 1+
Atoms lose an electron and become a positive ion.
Atoms gain electrons and become a negative ion.
4 protons: 4+ 3 electrons: 3- Charge: 1+
4 protons: 4+ 5 electrons: 5- Charge: 1-
(not from your text)
Functions of Ions
Generate Electricity (membrane potentials) • e.g., neurons of your brain and nervous system (sodium,
potassium, and calcium)
Regulate/initiate cellular events• e.g., help initiate muscle contraction, release of
neurotransmitters, expression of DNA, activate enzymes (calcium), blood clotting
Building materials• e.g., Calcium (and phosphate) is part of bones
Regulate pH/acidity • HCO3- (bicarbonate ion)
CHEMICAL BONDING AND MOLECULES
CHEMICAL BONDING
Two or more atoms can bind together to form a molecule.
There are 3 major types of chemical bonds• Ionic Bonds• Covalent Bonds• Hydrogen Bonds
Create molecules
do NOT create molecules
Ionic Bonds
Formation of an Ionic Bond
Covalent Bonds
When an electron pair is shared, both atoms get to “count” the other atom’s electron as if it was part of their own valance shell.
Covalent Bonds:• Atoms share electrons
• Strength:
Polar and Non-polar Bonds/Molecules
Non-Polar = electrons are shared equally • the entire molecule is neutral and uniformly charged.• Tends to mix well with other non-polar substances• Don’t mix well with water
Polar = electrons are not shared equally• then entire molecule is neutral overall, but has
regions/areas that are + or – charged• Tends to mix and dissolve well with other polar things• LIKES WATER/mixes with water
Polar (and charged)
HydrophilicWater soluble
nonpolar
HydrophobicNot water soluble
(lipid soluble)
Hydrogen bonds
Hydrogen BondsAre attractive forces between a hydrogen and an oxygen or a hydrogen and a nitrogen
• NOT based on electron transfer or sharing
Hydrogen bonds can exists between:1. two different molecules--resulting in their being held together.
2. two different parts of the same molecule— resulting in the bending/folding of the
molecule.
But hydrogen bonds don’t create molecules the way that a covalent or ionic bond does.
Comments on H-bonds
individual hydrogen bonds are weak, the collective influence of many hydrogen bonds can be significant• The bending of molecules with hydrogen bonds creates
the final 3D shape of proteins• Form between water molecules• Hold DNA strands together
H-bonds are weak bond formed between two polar molecules based on opposite charges attracting (not based on electron sharing)
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