protons electrons neutrons nucleus Center of the atom; contains protons and neutrons. The Atom Molecules are made up of two or more atoms.

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1 _ Period: The Atom Ch. 18:1 Everything is made of atoms. Atoms are the smallest part of matter. Atoms are made up of 3 subatomic particles (particles smaller than the atom): electrons, protons, and neutrons. n the following diagram of an atom define the parts of the atom. Negatively charged particles; outside the nucleus; can be gained or lost to and from other atoms; very small mass: 1/2000th of a proton electrons protons Positively charged particles; in the nucleus; determine what element an atom is. This model of the atom looks a lot like a solar system. The nucleus, which contain the protons and neutrons, in the center would be the sun. The electrons are the planets spinning around the nucleus. Neutral particles in the nucleus; give mass to the atom, but not charge. neutrons nucleus Center of the atom; contains protons and neutrons. Count the protons to tell what element this is: # of Protons: Element: John Dalton in 1808 published a theory of the atom that had these important points: All atoms of a particular element are the same. Atoms of different elements have different properties, mass, and chemical reactivity. Atoms are not changed by chemical reactions, just rearranged in order or number. Atoms, Molecules, and Compounds Atoms combine into molecules. is an atom; 2 is a molecule: both are oxygen. Molecules are made up of two or more atoms. If two different atoms combine they make compounds: H 2 is a compound; 2 is a molecule. Compounds are made up of two or more elements. Water molecule a compound (H 2 ) 2 hydrogens H 1 oxygen H xygen molecule an element ( 2 ) 2 oxygens Atom, molecule or compound? NaCl Cl 2 Na What elements are these? Na Cl

2 _ Period: Beginning to Read the Periodic Table Ch. 18:1 Reading the element individual tiles Element Name Chemical Symbol Mass Numbers (number of protons and neutrons in the nucleus of an isotope) Silver 47 Ag , 109 Different number of protons different element. Atomic Number (number of protons) Atomic Mass (units are a.m.u.) How much mass would 2 atoms of silver have? Different number of neutrons different isotope. An isotope is a variety of an element with a different number of neutrons. Use Your Periodic Table to Answer the Following Find the chemical symbols for these elements: Find the names for these elements: Find the atomic numbers for these elements: Find the atomic mass for these elements: Gold: Mg: xygen: H: Fluorine: N: B: Neon: Sulfur: He: Lithium: Al: 1. Proton a. Particles with no charge that exists in the nucleus of most atoms. 1. Atomic Number a. Total number of protons and neutrons in the nucleus of an atom. 2. Neutron 3. Electron 4. Nucleus 5. Atom b. Center of the atom, contains most of the atom s mass. c. Positively charged particle in the nucleus of the atom. Determines the element. d. The smallest part of an element or molecule. Building block of all things. e. Negative particles in the nucleus of the atom. f. Negatively charged particle that exists in the space around the nucleus. 2. Molecule 3. Compound 4. Mass Number 5. Isotope b. Number of protons in an atom; also the way the elements are numbered. c. An atom with a different number of neutrons d. Two or more elements combined. e. Two or more atoms that are combined (can be same two atoms of same element). f. Number of electrons in an atom.

3 Isotopes; Molecular Notation; Electron rbits Ch. 18:2 Isotopes An isotope is an element that has a different number of neutrons. As long as the number of protons is the same, it is still the same element. The isotopes of Hydrogen each has unique properties, but each is hydrogen, with only 1 proton. Protium 1 proton Deuterium 1 proton 1 neutrons Tritium 1 proton 2 neutrons Mass Number Remember that the mass number is the total number of masses (protons and neutrons) in the nucleus. Mass Number: number of protons and neutrons - Atomic Number: number of protons Number of Neutrons Ex. Tritium is Hydrogen with a mass number of 3. Find the number of neutrons. (Mass #) - (Atomic #) = (# of neutrons) 3-1 = 2 neutrons in Tritium Find the number of neutrons in Lithium 7. (Mass #) - (Atomic #) = (# of neutrons) Find the number of neutrons in xygen 18. Molecular Notation Chemical symbol for hydrogen Means 2 atoms of hydrogen H 2 No number means 1 atom of oxygen Chemical symbol for oxygen How many atoms of each element are there in CH 4? C carbon 1 atom H 4 hydrogen 4 atoms Total 5 atoms How many atoms of each element are there in C 2? Element # of atoms C: Carbon 2 : xygen Total: How many atoms of each element are there in NaH? Element Na: Sodium # of atoms : xygen H:Hydrogen Total:

4 Ch. 18:2 Electric Attraction + pposites attract - Electric charges work just like magnets: opposites attract and like charges repel. Since protons are positive and electrons are negative, protons attract electrons. Protons repel protons; electrons repel electrons. Like charges repel Though this may seem too simple, much of chemistry can be explained by electric attraction and repulsion. Q: If protons repel each other, how can a nucleus (made up of multiple protons) stay together? Electron rbits Because of electron-to-electron repulsion, electrons don t crowd around the nucleus as their number increase. Instead, they fill up orbits. Each orbit can hold a certain number of electrons, then that orbit is full. This is because even though as the number of protons increases (attraction), the number of electrons also increases (repulsion). hydrogen helium lithium sodium 1p 2p 2n 3p 3n 11p 12n 1 electron in first orbit 2 electrons; first orbit full 3 electrons; first orbit full; 1electron in outer orbit 11 electrons; two orbits full; 1electron in outer orbit BIG HINT: Each completed orbit (electron level) is one complete row on the periodic table. 1. Dalton 2. Bohr 3. Democritus 4. Rutherford 5. Thompson a. Did gold foil experiment which proved, in early 20th century, that atoms had a nucleus. b. Late 1800 s scientist found the electron and other smaller particles. c. Greek philosopher that realized said called the smallest part of matter atoms. d. Mid-1900s scientist that hypothesized that electrons are in distinct orbits. e. Scientist that said that atoms can be changed chemically. f. Worked with gases in 1808 and published theory that atoms were hard spheres. Magnesium has how many full electron levels (orbits)? Calcium has how many full electron levels? Neon has how many full electron levels:? Aluminum has how many full electron levels? Gold has how many full electron levels?

5 Periods and Groups; Valence Electrons; Masses Ch. 18:4 Periods and Groups Groups Elements that have the same number of outermost electrons have similar properties, so we put them in groups. n the periodic table groups = columns (up and down). You will use mostly groups 1A 18 A. Hydrogen is in the same group as Lithium. 1A 18A Elements that have electrons in the same electron levels are in the same period (row) on the Periodic Table. Periods go left and right. Helium is in the same period as Hydrogen. Periods H 3 Li 11 Na 19 K 4 Be 12 Mg 20 Ca Transition metals number of valence electrons varies 5 B 13 Al 31 Ga 6 C 14 Si 32 Ge Groups 2A 13A 14A 15A 16A 17A 7 N 15 P 33 As 8 16 S 34 Se 9 F 17 Cl 35 Br 2 He 10 Ne 18 Ar 36 Kr Thinking like the game Battleship, you can find an element by its period and group. What element is in Period 2 and Group 16A? Period 2 is row 2; Group 16A is Column 16A. The element is oxygen. What element is in Group 13A and Period 3? What element is in Group 2A and Period 2? What group and period is Chlorine in? Group: What about Magnesium? Group: Period: Period: Valence Electrons Valence Electrons are the outermost electrons in an atom. Each group (column) has the same number of valence electrons. Valence electrons are the electrons that are involved in chemical bonding. hydrogen 1 1p lithium 6 3p 3n oxygen 17 8p 9n xygen is in Group 16A and has 6 valence electrons. How many valence electrons will Sulfur have? 1 valence electron 1 valence electron 6 valence electrons How about Selenium? Hydrogen and Lithium are both in Group 1A both have 1 valence electrons. ctet Rule Atom are more stable that have a full shell of electrons. For most atoms (except H and He) this number is 8 (octet = 8). Atoms want to have 8 valence electrons. If I 8, I full. nly Group 18A have a full octet (8 valence electrons) naturally. All other elements will lose, gain, or share to reach 8 electrons.

6 Ch. 18:4 Using the Periodic Table The last digit of the Group (column) an element is in is its number of valence electrons. Helium is the one exception: Helium has 2 valence electrons. Ex. Neon is in Group 18A. The last digit of 18 is 8. Neon has 8 valence electrons. Beryllium is in Group 2A. Beryllium has 2 valence electrons. Find the valence electrons for the following elements: Sodium: Chlorine: Helium: Boron: Aluminum: Carbon: Calcium: Sulfur: Molecular Mass Remember: a.m.u. stands for atomic mass units (the unit for the mass of an atom). To find the mass of a molecule add up the masses of the individual atoms. NaCl = Na + Cl = ( ) = a.m.u R Na a.m.u. + Cl a.mu. NaCl a.m.u. If there are multiple atoms of an element, multiple by the number of atoms (or add up each atom individually). H 2 = H 2 + = (2 X 1.01) + (16.00) = ( ) = a.m.u. R H 1.01 a.m.u. H 1.01 a.m.u a.mu. H a.m.u. Don t forget units! Find the molecular mass of Mg. Find the molecular mass of C 2. Find the molecular mass of CH 4. Quick Review What element is K? How many protons does Copper have? Boron 11 has how many neutrons? What does P 4 stand for? How many atoms does AgN 3 have? How many full electron levels does Aluminum have? What scientist discovered that atoms have distinct energy levels? How did Rutherford find that atoms are mostly empty space and have a nucleus?