Periodic Table and Its Trends

Looking for the pattern with the elements

Metals Non-Metals Lab

What we some of the physical properties? chemical properties?

What are the characteristics of metals? Non-metals?

What are metalloids?

• Made the periodic table to organize elements - Too many elements to memorize so they classified them.

• Periodic: regular, repeating pattern

• Mendeleev: made first periodic table 1800s

• First table was by increasing atomic mass: the average mass of one atom of the element

Periodic Table

Mendeleev and table

•He made new rows each time properties repeated so the columns all had similar properties

•He left blank spots on table if properties didn’t match – all of his “blanks” have been discovered.

•The vertical columns are called groups

•The horizontal rows are called periods.

Modern Periodic Table

Do Activity on pg ?

Trends in periodic table

Many trends form in the periodic table when its organized by mass and atomic number:

From your card periodic tables:  plot of atomic number andCompounds formed:  Atomic number vs. oxygen in compounds

Periodic Table - Atomic Number

• The atomic number (on periodic table) shows the number of

protons.

oIts symbol is Z.

odetermines the identity of the element.

oThey are found in the nucleus

oAtoms are electrically neutral so atomic number

also shows number of electrons

Periodic table - Atomic Mass

•Atomic Mass/ Mass Number –

oSymbol is A.

oMass only includes protons and neutrons because

electrons are basically massless

oUnit is the “atomic mass unit” (amu) or u

•Rule of Thumb: The number of protons

determines the identity of the element

Number of protons +

neutrons

Isotopes and Atomic Number

•Scientists observed two kinds of neon atoms.

oexactly alike chemically, but different in mass.

oHe called them isotopes 2 minute movie clip

•Isotopes - Atoms of the same element that differ in

mass.

ohave the same number of protons but different numbers of

neutron.

omass difference is due to the number of neutrons in isotope

oIsotope names: element – mass eg Neon-20

Calculation /reading periodic table

To get protons – look at periodic table for atomic number

To get electrons - look at periodic table for atomic number

Calculations :

To get neutrons = mass number - atomic

number

To get Mass Number = protons + neutrons

Application

Complete this supplement. Make a copy and place in your handouts and activities folderSupplement 2A

You have 15 minutes to start this and ask questions.

Group 1: Alkali metals (not H) Group 2: Alkaline Earth Metals Groups 3-12: Transition metals Groups 13-15: No names/mixed groupsGroup 16: Chalcogens Group 17: Halogens Group 18: Noble Gases

Property trends

••Groups        of elements have similar properties.

••All alkali metals (group 1) are silvery white and explosive, form XCl as their chlorides and X2O as their oxidesoif Li forms Li2O with oxygen and Ca forms

CaO, what is the formula for what Sr will form with Oxygen?

Property trends continued

•You can estimate a property of an element by averaging the values of the elements above and below it.  

 

eg:  the density of silicon is 2.3 and the density of tin is 7.3.  estimate the density of germanium.

    look on periodic table and observe that Ge is between Si and Sn within a group.  Average the densities to get an estimate

 

        2.3  +  7.3   /   2   =  4.8

Group 1: Alkali metals (not H) – metals – have 1 electron on outer ring (1 valence electron) – gives it away to react and make + 1 ions Li1+ Group 2: Alkaline Earth Metals - metals – have 2 electron on outer ring (2 valence electron) – gives it away to react and make + 2 ions , Mg2+ Groups 3-12: Transition metals - give away electrons to reactGroups 13-15: No names/mixed groups – no trend since metals and nonmetals are mixed in these groupsGroup 16: Chalcogens - nonmetals – have 6 valence electrons, react by gaining 2 electrons , O2- Group 17: Halogens - nonmetals - have 7 valence electrons, react by gaining 1 electrons , F1- Group 18: Noble Gases – nonmetals, have 8 valence electrons, DO NOT REACT

 Do A11 Supplement

Electron pattern control element properties!!!