Introduction to the Periodic Table Atomic Number ● Symbol ● Atomic Weight Element ● Compound ● Mixture

Common Misconception Isotopes – atoms of the same element so they have the same ATOMIC # (protons) & different MASS # (neutrons) There is not just 1 “regular” atom which you see on the Periodic Table The symbols on the Periodic Table represent “average” atoms of elements A sample of an element found in nature contains a mixture of the different isotopes of that element

I made the PERIODIC TABLE ! I am Dmitri Mendeleev! I made the PERIODIC TABLE !

What is the PERIODIC TABLE? Shows all known elements in the universe. Organizes the elements by chemical properties.

How do you read the PERIODIC TABLE?

What is the ATOMIC NUMBER? The number of protons found in the nucleus of an atom Or The number of electrons surrounding the nucleus of an atom.

What is the SYMBOL? An abbreviation of the element name.

What is the ATOMIC MASS? The number of protons & neutrons in the nucleus of an atom.

How do I find the number of protons, electrons, and neutrons in an element using the periodic table? # of PROTONS = ATOMIC NUMBER # of ELECTRONS = ATOMIC NUMBER # of NEUTRONS = ATOMIC _ ATOMIC MASS NUMBER

The Periodic Law Elements are arranged by increasing atomic number (# of Protons)

Periodic Law Periods – Each row (7 total) Groups – Each column (32 total) 18 show up on our periodic table because the rows are pulled down Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups Pg 131 in the book fig. 6

Groups Elements in a group have similar electron configurations (valence electrons) Electron configurations determine its chemical properties (how they react) Members of a group in the periodic table have similar chemical properties Known as Periodic Law!!!

Elements, Compounds, and Mixtures

What is an ELEMENT? A substance composed of a single kind of atom. Cannot be broken down into another substance by chemical or physical means.

What is a COMPOUND? A substance in which two or more different elements are CHEMICALLY bonded together.

What is a MIXTURE? Two or more substances that are mixed together but are NOT chemically bonded.

Classes of Elements Solids, Liquids, or Gases Elements that occur naturally and those that do not – all but 2 w/ atomic # 1-92 occur on Earth naturally; elements # 93 & higher do not Metals, Nonmetals, and Metalloids Pg 133 in your textbook

Metals Good conductors of electric current and heat Except for Mercury, metals are solid at room temp.

Metals Most solids (Hg is liquid) Luster – shiny. Ductile – drawn into thin wires. Malleable – hammered into sheets. Conductors of heat and electricity. Include transition metals – “bridge” between elements on left & right of table

Transition Metals Elements that form a bridge between the elements on the left and right sides of the table Exp. Copper & Silver Many are able to form compounds with distinctive colors

Nonmetals Elements that are poor conductors of heat & electric current Exp. Fluorine is the most reactive

Non-Metals Properties are generally opposite of metals Poor conductors of heat and electricity Low boiling points Many are gases at room temperature Solid, non-metals are brittle (break easily) Chemical properties vary

Metalloids Elements with properties that fall between those of metals and nonmetals Ability to conduct electric current varies with temp.

Metalloids stair-step pattern Have properties similar to metals and non-metals Ability to conduct heat and electricity varies with temp Better than non-metals but not metals

Variation Across a Period: Left to Right Physical and Chemical properties Atomic size decreases Metallic properties decrease Ability to lose an electron decreases Ability to gain electrons increases

Review Elements are arranged by increasing Atomic Number (# of P’s) Each row = Period Each column = Group Properties of elements repeat in a predictable way when atomic #’s are used to arrange elements into groups

Review Continued… Atomic mass depends on the distribution of an element’s isotopes in nature an the masses of those isotopes Elements are classified as metals, nonmetals, and metalloids Across a period from left to right, the elements become less metallic and more nonmetallic in their properties