Organizing the Elements. Copper, Silver, and Gold 1700, 13 elements have been identified Rate of discovery increased..why? 1765-1775 Including.

THE PERIODIC TABLEOrganizing the Elements

Organizing the Elements

Copper, Silver, and Gold 1700, 13 elements have been

identified Rate of discovery increased..why?

1765-1775 Including hydrogen, nitrogen, and

oxygen

Organizing the Elements

Chemists used the properties of elements to sort them into groups.

Dobereiner (1780-1849)

Elements were grouped into triads.

Chlorine, Bromine, Iodine

Dobereiner’s Triads

Chlorine, Bromine, Iodine Physically completely different. Chemically react similar: react easily

with metals.

Organizing the Elements

1869-Mendeleev published his table of the elements.

More than 60 elements

Mendeleev arranged the elements in his periodic table in order of increasing atomic mass.

Mendeleev’s Periodic Table

Organizing the Elements

Based on chemical properties, arranging elements according to atomic mass only produced problems.

Elements that should have been grouped together weren’t, etc.

Mendeleev organized his table before the discover of protons and the assignment of atomic numbers to all of the elements.

Organizing the Elements

1913, Henry Moseley determined an atomic number for each known element.

In the modern periodic table, elements are arranged in order of increasing atomic number.

Modern Periodic Table

7 periods Periods correspond to energy levels.

Increase as the period number increases.

18 groups Elements within each group share

similar properties. Pattern changes from left to right.

Modern Periodic Table

Periodic Law

When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

Classes of elements: metals, nonmetals, and metalloids.

Metals 80 %

Sodium, iron, copper, any elements appearing in yellow.

Properties of metals: Conductors of heat and electricity High luster Solid at room temp Ductile malleable

Metals

Nonmetals

Identified in blue (red) Neon, carbon, nitrogen, oxygen Greater variation in properties: Gases at room temperatures, few are

solids like sulfur and phosphorus, and one liquid-bromine.

Brittle

Metalloids

Heavy stair step line separating metals and nonmetals. Identified as green (blue).

Metalloids have properties similar to metals and nonmetals.

Alter properties of metalloids by changing the conditions of the metalloids.

silicon

Classifying the Elements

Neon

Classifying by Group

Group IA - Alkali Metals

Group 2A – Alkaline Earth Metals

Group 7A- Halogens (Nonmetals)

Classifying by Electron Configurations

Electrons play a key role in determining the properties of elements.

Place elements in groups by the number of elements in the last orbital, or the number of valence electrons.

Noble Gases, Representative Elements, transition metals, and inner transmission elements.

Electron Configuration1A

2A 3A 4A 5A

6A 7A

8A

Noble Gases Group 8A

Inert Gases 8 electrons in last orbit Helium, neon, argon, etc

Representative Elements

1A-7A

Wide range of physical and chemical properties

Last orbital of electron cloud is not filled

Transition Elements

Group B

Transition Metals- presence of electrons in d orbitals

Displayed in the main body of the periodic table: copper, silver, gold, and iron

Inner transition metals- presence of electrons in f orbitals

AKA: rare earth elements

Electron Orbitals

Electron Sub-orbitals

Energy Levels

Classify by Energy Level

Noble Gases- Orbitals end in p, this will always be filled. Helium (He) will end in s2

Representative Element- orbitals end in s or p, these orbitals will NOT be filled.

Transition Elements-orbitals end with a combination of unfilled d orbitals and s orbitals.

Periodic Trends

Trends in Size

Atomic Radius-one half of distance between the nuclei of two atoms of the same element when the atoms are joined.

Atomic size increases from top to bottom within a group and decreases from left to right across a period.

Atomic Size

Atomic Radius

Ions

Atom or a group of atoms that have a positive or negative charge

Formed when electrons are transferred between atoms

Positive = cation, written as 1+ Negative = anion, written as 1-

Sodium Ion

Trends in Ionization Energy Energy required to remove an

electron from an atom

Decreases from top to bottom within a group, and increases from left to right across a period.

Trends in Ionization Energy

Trends in Ionic Size