Atoms & the Periodic Table

What is an Atom? Atom: Smallest unit of all matter 3 Main Parts: The Nucleus: 1) Proton (+) 2) Neutron (0) Electron Cloud 3) Electron (-) Protons & Electrons usually equal in number e e e

What is an Atom? Atom: Smallest unit of all matter 3 Main Parts: The Nucleus: 1) Proton (+) 2) Neutron (0) Electron Cloud 3) Electron (-) Protons & Electrons usually equal in number Elements (substance made of only 1 type of atom) are identified on the Periodic Table

Reading the Periodic Table Atomic Number: Number of protons the atom contains Usually the number of electrons also 6 C 12 Atomic Mass: Combined # of protons and neutrons inside the nucleus Electrons too small to affect mass 6 Protons = ______________ Electrons = ____________ Neutrons = _____________ 6 6

Reading the Periodic Table Atomic number: protons usually equal to electrons Atomic number: amount of protons 4 Be 9 Atomic mass: Protons + Neutrons 4 + ? 4 Protons = ______________ Electrons = ____________ Neutrons = _____________ 4 5

1 min: Discuss with your neighbor Atomic number: amount of protons 17 Cl 35 Atomic mass: Protons + Neutrons 17 + ? 35 a. What is the atomic mass of Chlorine? __________ b. What is the atomic number of Chlorine?__________ c. How many electrons does chlorine contain? __________ d. How many protons does chlorine contain? __________ e. How many neutrons does chlorine contain? __________ 17 17 17 18

He Electron Cloud 2 4 Electrons orbit the nucleus in “energy levels” 1st level: closest to nucleus stable w/ 2 electrons 2 1 2 He 4

Ne Electron Cloud 10 20 Electrons orbit the nucleus in “energy levels” 1st level: closest to nucleus stable w/ 2 electrons 2nd level: stable w/ 8 electrons 1 2 3 8 2 1 4 7 10 Ne 20 6 5

Ar Electron Cloud 18 40 Electrons orbit the nucleus in “energy levels” 1st level: closest to nucleus stable w/ 2 electrons 2nd level: stable w/ 8 electrons 3rd level: Atoms are stable when the outermost level is “full” 7 8 1 2 18 Ar 40 3 1 6 8 2 1 4 2 5 7 6 5 4 3

C Electron Cloud 6 12 Examine Carbon Is Carbon a stable atom? No. The second level lacks 4 electrons. 6 electrons 1 6 C 12 2 1 2 4 3

Molecules Molecule: 2 or more atoms held together by a chemical bond Form when atoms are unstable Two Main Types of Bonds: 1) Covalent Bond: Chemical bond where atoms share electrons Ex: Oxygen (O2) Why unstable? Only 6 electrons in outer energy level What happens? Oxygen atom will share two electrons with neighboring oxygen atom End result? Both end with 8 electrons in outer level (stable) Molecules 8 protons 8 electrons 6 Oxygen Nucleus 5 1 1 2 2 4 3

Molecules Molecule: 2 or more atoms held together by a chemical bond Form when atoms are unstable Two Main Types of Bonds: 1) Covalent Bond: Chemical bond where atoms share electrons Molecules Why unstable? Only 6 electrons in outer energy level What happens? Oxygen atom will share two electrons with neighboring oxygen atom End result? Both end with 8 electrons in outer level (stable) 6 6 Oxygen Nucleus Oxygen Nucleus 5 5 1 1 1 1 2 2 2 2 4 4 3 3

C Molecules Molecule: 2 or more atoms held together by a chemical bond Form when atoms are unstable Two Main Types of Bonds: 1) Covalent Bond: Chemical bond where atoms share electrons Molecules C Why unstable? Only 6 electrons in outer energy level What happens? Oxygen atom will share two electrons with neighboring oxygen atom End result? Both end with 8 electrons in outer level (stable) 6 6 Oxygen Nucleus 5 5 1 1 1 1 2 2 2 2 4 4 3 3

Molecules Molecule: 2 or more atoms held together by a chemical bond Form when atoms are unstable Two Main Types of Bonds: 2) Ionic Bond: chemical bond where electrons are gained/lost Held together by magnetic attraction Cause: 1 atom steals an electron(s) from another atom Ion: atoms with + or – charge Ex: Sodium + Chlorine = Sodium Chloride Molecules

Na Cl 11 17 23 35 Ionic Bonds +11 +17 -11 -10 -18 -17 +1 -1 Na Cl Na e e Stable Unstable Na e e Cl e e Stable Unstable e e e e e e Na+ e sodium e e Cl- e e e e chlorine e e e e e e e e e 11 protons 11 electrons 17 protons 17 electrons Before bonding After bonding Na Cl Protons (+) Electrons (-) Net charge 11 Na 23 17 Cl 35 +11 +17 -11 -10 -18 -17 +1 -1

Review Name the 3 subatomic particles. Which subatomic particles are found inside the nucleus? The atomic number usually allows us to determine the amount of which two subatomic particles? If an atom has the atomic mass of 14 and the atomic number of 6, how many protons, neutrons, and electrons does the atom contain? After an ionic bond is formed, what is the charge of the atom that gained an electron? Which type of chemical bond shares electrons?