ATOMIC STRUCTURE Democritus - Greek philosopher coined the term “atom” - unable to be divided Suggested atoms make up matter in 4th century BC He was unable to provide evidence that atoms really existed.

1808 - John Dalton All elements are composed of tiny particles called atoms. Atoms can’t be divided. 2. Atoms of the same element are identical. 3. Atoms can join together to form compounds. Chemical reactions occur when atoms are separated from each other, joined, or rearranged in different combinations.

Composition of an Atom Nucleus - center of the atom protons - positive particles neutrons - no charge electrons - negative particles - move around the nucleus

SUBATOMIC PARTICLES Particle Charge Mass Location Proton + 1 amu nucleus Neutron Electron - ~ 1/2000 amu outside

Bohr Model Electrons orbit nucleus like the planets orbit the sun Electrons path defines its energy level Electrons gain energy as they move farther from the nucleus

Wave/Quantum Mechanical Model Electrons behave like waves on a vibrating string (de Brolie). We cannot determine their exact location, only their atomic orbital, the region where they are likely to be found. Energy levels of electrons are labeled by principle quantum numbers (n).

Wave/Quantum Mechanical Model For each principle quantum number greater than one, there are energy sublevels. Each energy sublevel corresponds to one or more orbitals of different shapes. The orbitals describe where an electron is likey to be found.

Wave/Quantum Mechanical Model

Wave/Quantum Mechanical Model Principle # of Type of Maximum # Energy Level Sublevels Sublevel of electrons n = 1 1 1s (1 orbital) 2 n = 2 2 2s (1 orbital) 2 2p (3 orbitals) 6 = 8 n = 3 3 3s (1 orbital) 2 3p (3 orbitals) 6 3d (5 orbitals) 10 = 18

Wave/Quantum Mechanical Model Valence electrons - electrons in the outermost energy level

QUIZ-1 1. List 4 points of Dalton’s atomic theory. 2. What is the charge of an electron? 3. Why does the atom have no electrical charge? 4. What subatomic particles make up the nucleus of the atom? 5. Whose atomic model is known as the planetary model?

6. Whose atomic model is described as the plum pudding model? 7. Explain the modern wave/quantum mechanical atomic model. 8. Draw a model of the atom with 6 protons and 4 neutrons. 9. How many valence electrons does the atom you drew in question 8 have? 10. Energy levels of electrons are labeled by _____________.

THE PERIODIC TABLE Periodic Law - When elements are put in order of their atomic number, similarities in their properties occur in a regular pattern. Elements are arranged in order of increasing atomic number.

Periods – there are 7 horizontal rows - patterns can be seen from left to right across the period - Elements become less metallic Each row corresponds to a principle energy level. Group or family - vertical columns - elements in the same group have similar chemical and physical properties

Ion - charged atom Periodic Table can determine the charge, ex. Group 1A elements charge is (1+), Group 7A elements charge is (1-) Positive ions - lose electrons Negative ions - gain electrons

Atomic number - number of protons - top of square Mass number - protons + neutrons - bottom of square Isotope- atoms of same element, have same # of protons, different # of neutrons

Average atomic mass - average mass found for that element in nature amu (atomic mass unit)- unit of mass for atoms

Classifying Atoms Metals - on left of the zigzag line - shiny, good conductors of heat and electricity - malleable - can be hammered into a thin sheet - ductile - made into thin wire

Nonmetals-right of the zigzag line - dull and brittle - poor conductors Semiconductors (metalloids) - on either side of the zigzag line - characteristics of both metals and nonmetals

METALS Alkali metals (group 1) - most reactive ex. Na (NaCl - salt) Alkaline-earth metals (group 2) - less reactive than alkali metals, but still reactive ex. Calcium compounds form hard shells of many animals, limestone, bones and teeth

Transition metals - less reactive than other metals -can be found alone (uncombined) in nature, ex. Gold -used to make jewelry (Ag, Au) - Cu - wiring, plumbing - Hg - thermometers (only metal that is liquid at room temperature)

NONMETALS Carbon - found in all living things - in its pure state is usually found as graphite (pencil “lead” Oxygen - vital to most living things Nitrogen - fertilizer - 79% of air

Halogens (group 7A) - salt formers Chlorine - in bleach, a disinfectant Iodine - helps thyroid gland function properly Fluorine - in water, toothpaste (helps prevent tooth decay)

NOBLE GASES (group 8A) -inert (don’t react) -unreactive because their electron shell is full -ex. Neon - used in lights Helium - balloons

SEMICONDUCTORS Boron - added to steel to increase its hardness and strength Antimony - a fire retardant Silicon - found in sand (SiO2) - silicon chips (LED screens, computers)

QUIZ-part 2 What are the horizontal rows in the periodic table called? 2. What are the columns in the periodic table called? 3. Define isotope. What is the difference between atomic number and mass number? 5. State the periodic law.

QUIZ-part 2 continued 6. What is the group name of the most active metals? 7. What is another name for metalloids? 8. Give 3 characteristics of metals. 9. Give 2 characteristics of nonmetals. 10. What is the name of the group 2 metals? 11. List 2 places where calcium is found.

12. What does the word halogen mean? 13. What element makes up about 80% of air? 14. What does the word inert mean? 15. List an example of a transition metal and give a use of it.