Atoms and Molecules

Atoms Atoms are basic building blocks of matter. Democritus- developed the theory that atoms made all matter in 450 B.C

Atoms John Dalton- proposed the atomic theory of atoms All atoms of an element are alike No to elements have the same atoms Atoms cant be broken into smaller pieces Atoms combine to make compounds Every atom of an element has the same mass The masses of atoms in a compound must be equalized Found not to be true

Atoms J.J. Thompson- said atoms were a ball of positive charges with negative charges scattered throughout

Atoms Smallest unit of matter but not the smallest particle of matter Made of: Protons- have mass and a + charge Electrons- have very little mass and a - charge Neutrons- have about the same mass as a proton but have no charge

Atoms Ruthorford- found the positively charged center of the atom called the nucleus (it contained + charged protons)

Niels Bohr Father of the atomic model used today. Electron cloud Cloud Model

Molecules A molecule is the smallest particle of a substance that exists alone. This is a picture of a water molecule. It is two parts hydrogen and one part oxygen.                   

Compounds A compound is two or more elements combined together. This is a picture of a salt compound.

Name the charge of each part of an atom (whether it’s negative or positive). Proton Neutron Electron

Elements and the Periodic Table

Elements An element is a substance made up of only one kind of atom. Song

Classification is arranging items into groups or categories according to some criteria.

Classifying Matter

Review Matter is usually defined as anything that has mass and occupies space.

Gas Liquid Solid Disorder Some space Order Particles closer together Order Particles fixed in position Total disorder Lots of empty space Gas Liquid Solid

Review Solids, Liquids, and Gases Gases have no defined shape or defined volume Low density Liquids flow and can be poured from one container to another Indefinite shape and takes on the shape of the container. Solids have a definite volume Have a definite shape.

Mixtures and Pure Substances A mixture has unlike parts and a composition that varies from sample to sample A heterogeneous mixture has two or more dislike parts. A homogeneous mixture is the same throughout the sample

A classification scheme for matter.

Review A physical change is a change that does not alter the identity of the matter. A chemical change is a change that does alter the identity of the matter. A compound is a pure substance that can be decomposed by a chemical change into simpler substances with a fixed mass ratio An element is a pure substance which cannot be broken down into anything simpler by either physical or chemical means.

Sugar (A) is a compound that can be easily decomposed to simpler substances by heating. (B) One of the simpler substances is the black element carbon, which cannot be further decomposed by chemical or physical means.

Elements

Names of Elements The first 103 elements have internationally accepted names, which are derived from: The compound or substance in which the element was discovered An unusual or identifying property of the element Places, cities, and countries Famous scientists Greek mythology Astronomical objects.

The elements of aluminum, Iron, Oxygen, and Silicon make up about 88 percent of the earth's solid surface. Water on the surface and in the air as clouds and fog is made up of hydrogen and oxygen. The air is 99 percent nitrogen and oxygen. Hydrogen, oxygen, and carbon make up 97 percent of a person. Thus almost everything you see in this picture us made up of just six elements.

MODERN ATOMIC THEORY

The rest, that have permanent names have two letters. Chemical Symbols There are about a dozen common elements that have s single capitalized letter for their symbol The rest, that have permanent names have two letters. the first is capitalized and the second is lower case. Some elements have symbols from their Latin names. Ten of the elements have symbols from their Latin or German names.

Atomic Number Charge (if ion) Symbol Atomic Mass

Cs 55 133 EXAMPLE Atomic number = protons and electrons How many protons, neutrons and electrons are found in an atom of 133 55 Cs Atomic number = protons and electrons There are 55 protons and 55 electrons Mass number = sum of protons and neutrons 133 – 55 = 78 There are 78 neutrons

Hydrogen Protons: Neutrons: 0 Electrons: H 1 1

Sodium Protons: 11 Neutrons: Electrons: 11 Na 23

Rhenium Protons: Neutrons: Electrons: 75 75 Re 186

Rhenium isotope Protons: 75 Neutrons: 112 Electrons: 75 75 Re 187

The Periodic Law

Things to look for Explain the properties of metals. What are the noble gasses? What makes a metalloid different from a non- metal? How do you calculate the atomic mass of an element? What are the locations of the alkali metals, the earth metals, the halogens, and the noble gasses?

The Periodic Law Similar physical and chemical properties recur periodically when the elements are listed in order of increasing atomic number.

The Modern Periodic Table

Introduction A row is called a period A column is called a group

Chemical “Families” IA are called alkali metals because the react with water to form an alkaline solution Group IIA are called the alkali earth metals because they are reactive, but not as reactive as Group IA. They are also soft metals like Earth. Group VIIA are the halogens These need only one electron to fill their outer shell They are very reactive. Group VIIIA are the noble gases as they have completely filled outer shells They are almost non reactive.

Four chemical families of the periodic table: the alkali metals (IA), the alkaline earth metals (IIA), halogens (VII), and the noble gases (VIIIA). Alkaline metals- very reactive Earth metals- reactive Halogens- slightly reactive Noble gases- unreactive

Metal: Elements of the left side of the periodic table that are usually solids at room temperature, conduct heat, can be bent, and are shiny. Non-Metal: Elements in the upper right corner of the periodic Table. Relatively unreactive Metalloid: Elements that lie on a diagonal line between the Metals and non-metals. Their chemical and physical properties are intermediate between the two. Conductive , brittle, solid, slightly reactive

Properties of Metals Malleable- can be bent, hammered, and rolled Ductile- can be drawn into strands Magnetic

Review Horizontal rows are called periods Atomic number is the number of protons Atomic mass is the number of protons + neutrons (average) Mendeleev made the first periodic table Chemical symbols are made of 1-2 letters Neutrons have no charge Electrons have a negative charge Shared Electrons are the electrons shared between two atoms that are combined

Ticket Out Choose One of the following questions to answer Explain the properties of alkali metals, and where are they located? What are the noble gasses, and where are they located? What makes a metalloid different from a non- metal? How do you calculate the atomic mass of an element?