The Particle Theory
of Matter
VA SOL PS 2a,b
Elements, Compounds, Mixtures
What is the smallest particle?
Video hyperlink
O A piece of sand?
O A bit of dust floating in the air?
O What is it made of?
O If it is too small for you to see, does it still exist?
O School microscope? Electron microscope?
O Divide that dust into a hundred pieces
O A thousand pieces? A millions pieces?
O A BILLION pieces??
Sub-Atomic Particles
The Atom
O The basic particle from which all elements
are made
O Elements are pure substances that can be
found on Earth.
O An atom is one particle of an element
O 92 elements occur naturally, 26 more have
been produced in science labs
O Ex: oxygen, gold, sulfur
Nanoscale!
Quarks
O There are particles even smaller than atoms, but
they don’t make elements – they make atoms!
O Those smaller particles are
O Quarks – they have really weird names!
O Up, Down, Top, Bottom, Strange, & Charm
O Leptons
O Electron, Muon, Neutrino, & Tau
Proton
O 2 up quarks and 1 down quark make a proton
O Proton – the most important particle in an atom
O The number of protons in an atom determine which
element it is. Called atomic number
O 1 proton = hydrogen
O 6 protons = carbon
O 8 protons = oxygen
O 26 protons = iron
O Has a positive electrical charge (+)
Neutron & Isotope
O 2 down quarks and 1 up quark make a neutron
O Neutron – found in nucleus of atom with proton
O A neutron does not have an electrical charge – neutral
O The number in a nucleus can change.
O Carbon 12 = 6 protons & 6 neutrons
O Carbon 13 = 6 protons & 7 neutrons
O Carbon 14 = 6 protons & 8 neutrons
O Called isotopes (like flavors of ice cream)
O When they are not equal, this causes the atom to be
radioactive – it breaks apart
Electron & Ion
O Electrons are not made of anything smaller
O Has a negative electrical charge (-)
O There is usually 1 electron for every proton
O 1 proton + 1 electron
O Like neutrons, that number can change
O When an atom loses or gains an electron, it is no
longer called an atom, it is now an ion.
O Losing an electron makes the atom have a positive
charge (+). Its called a cation. (ACID)
O Gaining an electron makes the atom have a negative
charge (-). Its called an anion. (BASE)
Nucleus
O Protons and neutrons are together in the
center of the atom.
O It is called the nucleus
O Electrons spin rapidly around the outside of
the nucleus.
O They form layers – like the layers of an onion
O These layers are called “orbital shells”
Atomic Structure
Nucleus
Molecule
O Whenever 2 or more atoms are connected, it is
called a molecule
O It can be 2 or more atoms of the same element
O O is an atom of oxygen
O O2 is a molecule of oxygen
O Or it can be 2 or more elements of a different
element
O CO2 is a molecule of carbon dioxide
Compound
O When 2 or more atoms of different elements are
hooked together, it is called a compound
O 2 atoms of hydrogen + 1 atom of oxygen = a
molecule of H2O (water)
O 1 atom of sodium + 1 atom of chlorine = a molecule
of sodium chloride (NaCl or salt)
O These are chemically bonded together. They can
not be physically separated
O Only a chemical reaction can break the bonds
Mixture
O Mixtures are 2 or more elements or compounds that
are physically mixed together
O They can be easily separated
O There are 2 kinds of mixtures
O Heterogeneous mixtures – you can see the different
substances. Ex: Trail Mix, a salad, or a messy locker
O Homogeneous mixtures – you cannot see the different
substances. Ex: Kool-Aid, milk, or air
Solution
O Solutions are a type of homogeneous mixture
O When one substance is dissolved in another
O Ex: sugar dissolved in water
O Solvent – what does the dissolving (water)
O Solute – what gets dissolved (sugar)
O Water dissolves more substances than anything else
O Called the Universal Solvent
Solubility
O Solubility is a measure of how much solute can
dissolve in a solvent
O Ex: how much sugar can dissolve in water?
O Affected by temperature
O Hotter? More sugar will dissolve
O Colder? Less sugar will dissolve
O A solution is saturated when no more solute will
dissolve in the solvent
O If hot sugar water with a LOT of sugar in it is cooled
down, then the sugar will precipitate out (fall down)