SECTION 1: THE PERIODIC TABLEChapter 19: Elements and their Properties

WARM-UPMany parts of our lives are affected by repeated patterns. For example, a calendar shows the patterns of weeks. Name some repeated patterns that you see happening all the time.

LEARNING GOALSExplain the composition of the periodic table.

Use the periodic table to obtain information.

Explain what the terms metal, nonmetal, and metalloid mean.

ORGANIZING THE ELEMENTSIn the late 1800s, Dmitri Mendeleev searched for a way to organize the elements.He arranged all of the elements known at that time in order of increasing atomic mass and discovered a pattern.

ORGANIZING THE ELEMENTSAll of the elements of the same color show similar properties.

ORGANIZING THE ELEMENTSWhen we arrange them in rows, similar properties align in the same column.

ORGANIZING THE ELEMENTSBecause this pattern repeated, it was considered to be periodic.

Periodic Table: a table that arranges the elements by increasing atomic number and by changes in physical and chemical properties.

ORGANIZING THE ELEMENTSMendeleev’s table was not perfect.Some elements on the current periodic table show decreasing atomic mass from left to right.

Henry Moseley arranged the elements based on atomic number instead.We still use this method today!

THE PERIODIC TABLEAll of the elements in the pink squares are metals.Ex: Iron, zinc, and copperMost metals are solids at room temperature

Shiny, can be drawn into wires, pounded into sheets, and are good conductors

THE PERIODIC TABLEAll of the elements in the green squares are nonmetals.Ex: Oxygen, bromine, and carbon

Most nonmetals are gasesMost are brittle, and are poor conductors of heat and electricity

THE PERIODIC TABLEAll of the elements in the purple squares are metalloids.Ex: Boron, silicon, and arsenicHave some properties of both metals and nonmetals

Also called semimetals

THE PERIODIC TABLEVertical columns of elements are called groups or families.Elements in the same group have similar chemical properties.

Horizontal rows of elements are called periods.Atomic number increases across a period.

ELECTRON CLOUD STRUCTUREElectrons are responsible for giving groups of elements similar properties.

In a neutral atom, the number of electrons is equal to the number of protons.A carbon atom has 6 protons and 6 electrons.

ELECTRON CLOUD STRUCTUREElectrons within the electron cloud have different amounts of energy.We model this difference by placing electrons into different energy levels.

ELECTRON CLOUD STRUCTUREEnergy levels closest to the nucleus have lower energy than those in the outer energy level.

ENERGY LEVELSEnergy levels are named using the numbers 1-7.Each number corresponds to a row

on the periodic table.

ENERGY LEVELSHydrogen and Helium are in the first row.Their electrons only occupy energy

level 1Hydrogen has 1 electron in this levelHelium has 2 electrons in this level

ENERGY LEVELSEach energy level has a maximum number of electrons that it can holdEnergy level 1 can hold 2 electronsEnergy level 2 can hold 8 electronsEnergy level 3 can hold 18 electronsEnergy level 4 can hold 32 electrons

Once one energy level is filled, electrons start filling the next level.

ENERGY LEVELSIt is the number of electrons in the outer energy level that determines the chemical properties of the element. Valence electrons: the electrons that occupy the outermost energy level.

ENERGY LEVELSEven though each energy level can hold a different total number of electrons, the outermost energy level of an atom can only hold up to EIGHT valence electrons.

ENERGY LEVELSAll elements in the same group have the same number of valence electrons.

ELECTRON DOT DIAGRAMSHydrogen, lithium, and sodium all have one electron in their outermost energy level.We can show this relationship by

using electron dot diagrams.Electron dot diagram: uses

the symbol of the element and dots to represent electrons in the outermost energy level.

ELECTRON DOT DIAGRAMSPractice: draw the electron dot diagram for the following elements:Lithium (Li)Phosphorus (P)Bromine (Br)Argon (Ar)Strontium (Sr)Oxygen (O)

ELECTRON DOT DIAGRAMSThe elements in Group 17 have electron dot diagrams similar to chlorine:

Because all members of a group have the same number of valence electrons, they all undergo chemical reactions in similar ways.

ELECTRON DOT DIAGRAMSA common property of the elements in Group 17 is that they easily form compounds with elements from Group 1.

ELECTRON DOT DIAGRAMSSodium and chlorine come

together to form sodium chloride.

ELECTRON DOT DIAGRAMSNot all elements will combine readily with other elements.Elements in Group 18 have full outer energy levels.This causes these elements to be relatively unreactive.

CHECK-INWhat do all of the elements in a group have in common?