EQ: What are atoms? What are they made of? The Atom EQ: What are atoms? What are they made of?

The Building Blocks of Matter: Atoms - - - + + + + - - + + - - -

Atoms Smallest possible unit into which matter can be divided, while still maintaining its properties. Made up of: protons neutrons electrons - + - + + - + + - -

Atoms are so small that… it would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil from your kitchen. if you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3 cm in diameter – about the size of a ping-pong ball a human hair is about 1 million carbon atoms wide. a typical human cell contains roughly 1 trillion atoms. a speck of dust might contain 3x1012 (3 trillion) atoms. it would take you around 500 years to count the number of atoms in a grain of salt. www.deckersfoods.com C-C-C-C-C-… + 999,995 more 1 trillion atoms  . Is made of approximately 3 trillion atoms Just one of these grains

+ Protons (+) Positively charged particles Located in the NUCLEUS The identity of the atom…they NEVER change! Equal to the atomic number of the atom + - +

Neutrons Neutral particles; have no electric charge + - Neutral particles; have no electric charge Located in the NUCLEUS of the atom

- Electrons (-) Negatively charged particles Found outside the nucleus of the atom, in the electron shells Move so rapidly around the nucleus that they create an electron cloud Mass is insignificant when compared to protons and neutrons Involved in the formation of chemical bonds + - -

How Are Atoms Described? Atomic number = number of protons In a neutral atom, the # of protons = the # of electrons Atomic mass= the number of protons + the number of neutrons

What would be the atomic number of this atom? The number of protons in the nucleus of an atom - What would be the atomic number of this atom? + - -

Mass Number The total number of PROTONS + NEUTRONS in an atom’s nucleus Expressed in Atomic Mass Units (amu) Each proton or neutron has a mass of 1 amu - What would be the mass number of this atom? +  3  4 + - 3 protons + 4 neutrons = a mass number of 7 amu Why did we not account for the electrons when calculating the mass number? -

Short hand form AZ Notation Ex. AZ X A = mass number Z = atomic number X = Element Symbol So…126C shows that Carbon has an atomic number of 6 (6 protons) and a mass number of 12 (6 protons and 6 neutrons) 147N: How many protons? ____ Electrons? ____ Neutrons?__ 3216 S: Protons? _____ Electrons? ______ Neutrons? ____ 3517Cl: Protons? ______ Electrons? _________ Neutrons? _____

Isotopes All atoms of the same element have the same number of protons; however, atoms of the same element with different numbers of neutrons are called isotopes. Notice that each of these atoms have one proton; therefore they are all types of hydrogen. They just have a different mass number (# of neutrons). - - + + + - Hydrogen (Protium) Hydrogen (Deuterium) Hydrogen (Tritium)

Isotopic Notation… Atoms with extra neutrons are like a person born with extra fingers! Still human, but a little bit different! Often, atoms with extra neutrons are unstable and break apart (called radioactivity!). The more extra neutrons, the more unstable they are. Element Name – mass number OR Element Symbol – mass number For example, all carbon atoms have 6 protons (definition of carbon.) Most carbon atoms have 6 neutrons (mass number of 12.) Carbon – 12 OR C – 12 But some carbon atoms have 8 neutrons, giving them an mass number of 14. Carbon – 14 OR C-14

Atoms, Isotopes, & Ions Atom: no overall charge- neutral, the number of protons EQUALS the number of electrons. Isotopes: atoms of an element with the same number of protons, but different number of neutrons. Ion: carries a charge, the number of electrons DO NOT equal the number of protons. Protons don’t change, they are the IDENTITY of the atom Electrons are either gained or lost Gained: the overall charge is negative Lost: the overall charge is positive