Atomic Models

Democritus 430BC gave the atom it’s name. Atom: uncuttable Dark Ages no further work has been recorded The idea of atoms began to develop again in the 1600’s as people did experiments.

John Dalton’s Atomic Theory 1776 Atoms 1)Consist of elements that cannot be divided 2)All atoms of same element are exactly alike and have the same mass. 3)An atom of one element cannot be changed into an atom of another element. 4)Compounds are formed when atoms of more than one element are combined.

J.J. Thomsen’s model (1897) Plum pudding or watermelon model Discovered atoms contain charged particles, positive and negative. Positive charge must balance negative charge.

Ernest Rutherford 1911 Discovered that atoms are mainly empty space with a positively charged nucleus. His new model is like a cherry. The dense nucleus surrounded by empty space. Protons are in the nucleus.

Niels Bohr’s Model 1913 Electrons are found in specific energy levels or orbitals. Each possible orbit has a fixed energy. Electrons furthest from the nucleus have the highest energy.

Modern Model 1932 Electrons move rapidly within a “cloud” around the nucleus. Nucleus contains protons and neutrons. Clouds contain electrons

Atomic model videos History of atom short version Thomsen’s experiment History of atom long version Rutherford’s experiment

Periodic Table Organizes the elements by atomic number, mass and families. Mendeleev built the periodic table in the 1800’s.

Counting Particles Atomic Number Tells you the number of protons and electrons in an element

Atomic Mass Atomic mass tells you the weight of each nucleus. Nucleus mass = protons + neutrons Each mass is written in atomic mass units (a.m.u.)

How to find # of neutrons To find # of neutrons, subtract the atomic mass from the atomic # and round. For example Oxygen = (16) – atomic # (8) = 8 neutrons

Models of atoms Model the atoms nucleus and place electrons in an orbit

Neutrons The bigger the element the more neutrons you will have. The neutrons hold the nucleus together. How many neutrons would gold have?

Isotopes Isotopes of an element have same number of protons, different number of neutrons. That is why atomic mass has decimal parts. The mass is a weighted average like grades.

Isotopes Abundance is how common it is to find in nature. You multiply the weight by the abundance to get the weighted average.

Nuclear fusion on sun

Patterns of the periodic table Rows = periods Each period goes from metals to metalloids to nonmetals.

Real periodic table

Cylinder periodic table

Groups of the periodic table Groups are known as families Elements in each family have similar chemical properties. The elements in a family all have the same valence (outermost) # of electrons.

Alkali metals Most reactive metals in the periodic table. Never found uncombined in nature Have 1 valence electron Sodium (salt) reactivity of alkali metals

Alkaline Earth Group 2 elements Less reactive than alkali metals, but still reactive. Calcium – found in bones, teeth Have 2 valence electrons alkaline earth metals

Transition Metals Groups 3-12 Iron, copper, gold, nickel, silver Hard and shiny solids, except mercury at room temperature. Good conductors of heat and electricity. Less reactive than Group 1 or 2

Properties of metals All metals transfer electrons to become stable when they are reacted with a nonmetal.

Metalloids Some properties of metals and some of nonmetals. Solids at room temperature Conductivity most important property. Silicon and germanium are used to make chips for computers/cellphones etc.

Nonmetals Groups Lacks most of the properties of metals. Poor conductors of heat and electricity Brittle as solids Many are gases at room temperature Carbon, Sulfur, and iodine are solids at room temperature

Properties Gain or share(covalently) electrons to become stable. When metals bond with nonmetals the metal transfers it’s electrons to the nonmetal. i.e. salt When nonmetals bond with nonmetals the elements share electrons. i.e. water

Jigsaw Element Project You are to choose one of the elements in your family. You will need to make a visual aid (2D or 3D) of your element and use to present to the class. All information required must be included in your poster/ and or presentation. You will present as a group, each person must have a part.

Requirements Atomic Symbol (atomic number, atomic mass) # of protons, electrons, and neutrons Correct model of atom Physical properties of the element # of valent electrons in family Common uses of the element and/or compounds made from the element. Similarities and differences to other elements in the family.

Rubric Visual aid Contains required information20 pts. Follows ABCD10 pts. (accurate, big, colorful, detailed) Group work10 pts. All group members were on task and used class time wisely. Group met the timeline10 pts.

Rubric Continued Presentation All group members presented10 pts. Voices/Eye Contact(average)10 pts. Attentive to other presentations10 pts.

Timeline You will have two days and the weekend to get your project done and presented.

Carbon Family

Nitrogen family

Oxygen Family

Halogen family

Noble Gases

Metalloids