the nature of matter
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The Nature of Matter. Chapter 2. Atoms. Smallest particle of an element Structure of the atom Nucleus: Protons (+) Neutrons (no charge) Orbital cloud: Electrons (-) Move rapidly can be gained or lost Outer levels have a higher energy. Atoms. Duet rule: - PowerPoint PPT PresentationTRANSCRIPT
The Nature of Matter
Chapter 2
Atoms
Smallest particle of an element Structure of the atom
Nucleus: Protons (+) Neutrons (no charge)
Orbital cloud: Electrons (-)
Move rapidly can be gained or lost
Outer levels have a higher energy
Atoms
Duet rule: the closest orbital around the
nucleus can hold 2 electrons Octet rule:
the cloud orbitals can hold up to 8 electrons
This causes attraction between atoms
Atoms
Neon atom 10 protons 10 neutron 10 electrons
Duet Rule
Octet Rule
Stable element
Atoms
Charge of the atom Sum of protons and electrons
If number of protons = number of electrons no electrical charge
Atoms
Ion: charged particle lose or gain electron
Cl- (gained 1 electron)
Na+ (lost 1 electron)
Ca2+ (lost 2 electrons)
Elements
Element Substance that cannot be
chemically broken down further
Consists of entirely one atom
Elements
Mass of the atom Sum of protons and
neutrons Atomic #
Number of protons
Isotopes
Isotopes Amount of protons ≠
number of neutrons Can be more or less Atomic mass is average
masses of element’s isotopes
Isotopes
Radioactive isotopes Unstable nucleus and break down at a
known rate over time Give off radiation which may be dangerous Many uses in science
Tracers to follow movement within organisms
Ex: Carbon-14 can be used to detect the age of ancient bones
Chemical Compounds
Compound Substance that can be broken
down to elements (2 or more elements)
97% of all compounds contain only 6 elements
C-H-O-N-P-S C-H-O-N = 64%
Chemical Bonds
Atoms in compounds are held together by various types of bonding
Which part of the atom is involved in bond formation?
Bonds form by using valence electrons
What types of bonds are there? Ionic and covalent
Ionic Bond
Ionic bond Electrons are transferred Attraction between oppositely
charged ions Ex: Na transfers e- to Cl Na+Cl- Become charged particles by
gaining or losing electrons
Covalent Bonds
Covalent bond Pairs of electrons in outer shell
shared by both atoms Can be single (2 electrons) or
double (4 electrons)
States of Matter
Solid Maintains fixed volume and shape Atoms are more likely linked to each other
Liquid Maintains a fixed volume Particles move more frequently Ability to flow and change into any shape
Gas Particles move rapidly Fill volume of container occupied
Chemical Reactions
One or more substances is made or broken down
Reactants On the left side of an equation Starting substance(s)
Products On the right side of an equation Ending substance(s)
CO2 + H2o H2CO2
Activation Energy
Energy needed in order for a reaction to occur
Substances known as catalysts can lower the activation energy to make a reaction start faster Living things have catalysts are called enzymes that
speed up reactions
Demonstration
Are the pieces of paper without water more attracted to each other?
Why are the pieces of paper with water easier to stick together?
What is holding the papers together? Water is a polar molecule Partial negative pole and partial positive
side
Polarity
An uneven distribution of charges within a molecule
In a water molecule the oxygen atom has a greater ability to attract electrons to it, which pulls the hydrogen atoms to one side
Hydrogen bonding
Due to partial positive and partial negative poles on the water molecule, other water molecules are attracted to each causing a hydrogen bond
Not as strong as covalent or ionic bonding
Hydrogen Bond
http://programs.northlandcollege.edu/biology/Biology1111/animations/hydrogenbonds.html
What are the other unique properties of water?
Cohesion: The ability for water to be attracted to itself
Cohesion – Surface Tension
Adhesion - The ability for water to be attracted to other substances
Adhesion - Capillary Action
How water moves up plants
Plant tubes (xylem) are made of cellulose which is polar
Water molecules are attracted to the sides of thin tubes of xylem
What do you think will happen to the daisies?
Capillary Action
How water moves up plants
Water molecules are attracted to the sides of thin tubes plant walls
This is also why water moves up a straw without you doing anything!
Activity!
Drops of water on a penny
What properties of water are shown in this experiment?
pH
pH is the concentration of hydrogen ions in a solution
It is the “potential of Hydrogen”
Strong Acid and Base
HCl – hydrochloric acid Strong acid Solution would have a HIGH concentration of H+
ions H+ loses electron to Cl-
NaOH – sodium hydroxide Strong base Solution would have a HIGH concentration of OH-
ions Na+ loses electron to OH-
Buffers
Weak acids/bases that react with strong acids or bases to have a gradual shift in the pH scale
Ex: Milk calming stomach acid
Why is water neutral?
The molecule of H2O separates into H3O and OH- H+ loses electron to OH- Equal parts of each ion H2O has a neutral pH of 7
pH scale