Periodic Table Chapter 5 Development of the Periodic

Periodic Table Chapter 5

Development of the Periodic Table � Dmitri Mendeleev (1834 -1907) – first person to organize the elements in a chart ◦ Arranged ~ 70 elements by increasing atomic mass ◦ Left blank spaces for elements which were not discovered yet

Development of the Periodic Table � Henry Moseley (1913) – rearranged Mendeleev’s periodic table ◦ Arranged elements by increasing atomic number ◦ Also grouped elements by their properties ◦ Current configuration of the Periodic Table

Modern Periodic Table �Elements are arranged by atomic number ◦ Columns = groups/families ◦ Rows = periods �Periodic Law: periodic repetition of physical and chemical properties

Groups of the Periodic Table �Alkali Metals (group 1) ◦ React Violently with water �Lithium �Sodium �Potassium �Rubidium �Cesium �Francium

Groups of the Periodic Table �Alkaline Earth Metals (group 2) ◦ Very common in the earth’s surface �Beryllium �Magnesium �Calcium �Strontium �Barium �Radium

Groups of the Periodic Table �Transition Metals (Groups 13 -16) ◦ Most of the common metals �Inner Transition Metals ◦ Lanthanide & Actinide Series

Groups of the Periodic Table �Halogens (group 17) ◦ Highly reactive �Fluorine �Chlorine �Bromine �Iodine

Groups of the Periodic Table �Noble Gases (group 18) ◦ All gases ◦ Do not react or combine with any other element

LAB: Metals, nonmetals, metalloids Determine physical and chemical properties

Metals, Nonmetals, metalloids � Line of Demarcation: jagged “stairs” which separate the left and right side ◦ Metals = left and below the line of demarcation ◦ Nonmetals = right and above the line of demarcation ◦ Metalloids = B, Si, Ge, As, Sb, Te

Metals, Nonmetals, metalloids �Properties of Metals ◦ Conduct electricity & heat ◦ Malleable ◦ Strong ◦ High melting and freezing points ◦ Mostly solids ◦ Have Luster

Metals, Nonmetals, metalloids �Properties of Nonmetals ◦ Insulators – do not conduct well ◦ Brittle ◦ Low melting and freezing points ◦ Contain gases and liquids ◦ Are dull

Metals, Nonmetals, metalloids �Properties of Metalloids �have properties of both metals and nonmetals �Ex) Silicon ◦ -semi-conductor ◦ -brittle

Atomic Structure A further look into the periodic table

The Atom: From Philosophical Idea to Scientific Theory � Democritus (Greek philospher; 450 BCE) ◦ First suggested the idea that atoms existed but had no experimental support ◦ Atom: the smallest particle of an element that keeps the properties of that element. �(Greek: atomos = indivisible)

The Atom: From Philosophical Idea to Scientific Theory Dalton’s Atomic Theory 1. All elements are composed of tiny indivisible particles called atoms.

The Atom: From Philosophical Idea to Scientific Theory Dalton’s Atomic Theory 2. Atoms of the same element are identical. The atoms of one element are different from those of another.

The Atom: From Philosophical Idea to Scientific Theory Dalton’s Atomic Theory 3. Atoms can combine with other atoms in whole number ratios. H 2 O C 12 H 22 O 11 NOT H 2. 5 O¾

The Atom: From Philosophical Idea to Scientific Theory Dalton’s Atomic Theory 4. Chemical reactions occur when atoms are separated, joined or rearranged. Atoms are not changed into atoms of another!

The Atom: From Philosophical Idea to Scientific Theory Dalton’s Atomic Theory 5. Atoms can not be subdivided. ◦ we now know atoms can be divided into smaller parts

Can you tell me the 5 parts of Dalton’s Atomic Theory?

Our understanding of the atom has changed

Dalton’s atom �A simple sphere with no internal structure � The way compounds were held together was poorly understood

Discovery of the Electron � Discovered by J. J. Thomson (1897) (e ) ◦ “Cathode Ray” experiment ◦ Negatively charged subatomic particles called electrons responsible for the ray were attracted to the positive end of a magnet ◦ Plum Pudding Model

Discovery of the Proton � Discovered by Goldstein (1886) + (p ) ◦ Positively charged subatomic particles called protons ◦ 1, 840 times heavier than an electron

Discovery of the Neutron (no) � Discovered by James Chadwick (1932) ◦ Subatomic particles with no charge called neutrons ◦ Mass is nearly the same as a proton

Discovery of the Atomic Nucleus � Discovered by Rutherford (1911) ◦ Gold Foil Experiment �nucleus of an atom = small dense positively charged center BBC Video Gold Foil Expt

Discovery of Electron Orbits � Discovered by Bohr (1912) ◦ Electrons orbit the nucleus in definite energy levels

Summary of Subatomic Particles Particle Electron Proton neutron Symbol Relative Charge Location in the atom

Atomic Number � Definition = the number of protons in the nucleus of an atom of an element � also equals the # of electrons (because atoms are neutral) � Periodic Table ◦ How many p+? ◦ How many e-?

Mass Number � Definition –total # of protons and neutrons in an atom � Remember… ◦ Protons and neutrons have the same relative mass ◦ All of the mass of an atom comes from its protons and neutrons � Mass numbers are ALWAYS whole numbers ◦ To use the periodic table, round the atomic mass Mass Number? ? ?

Determining # of particles �# of protons = atomic number �# of electrons = # of protons �# neutrons = Mass # - Atomic # (in a neutral atom)

Determine the # of particles Symbol p+ n 0 e- Atomic # Mass #

Isotopes � Definition – atoms that have the same number of protons but different numbers of neutrons � Identified by mass number � Atomic # stays the same � Ex) Carbon – has 3 isotopes ◦ 1) Carbon – 12 ◦ 2) Carbon – 13 ◦ 3) Carbon – 14

IONS � Atoms with a charge (results from gain/loss of electron) � If an atom GAINS an electron = ANION ◦ Negative charge ◦ Ex: Cl- � If an atom LOSES an electron = CATION ◦ Positive charge ◦ Ex: Ca 2+

Ions � Examples: Symbol p+ n 0 e- Atomic # 6 11 S Mass # Charge 14 0 12 1+ 33 2 -

Isotopes of Carbon � All have the same # of p+ ◦ If not, it would be a different element ◦ All have 6 protons � 1) Carbon – 12 � 2) Carbon – 13 � 3) Carbon – 14 ◦ Has 6 neutrons ◦ Has 7 neutrons ◦ Has 8 neutrons

Isotopes of Hydrogen � Hydrogen-1: 1 p+ and 0 no � Hydrogen-2: 1 p+ and 1 no � Hydrogen-3: 1 p+ and 2 no ◦ Relative abundance = 99. 985 % ◦ Commonly called normal “hydrogen” ◦ Relative abundance = 0. 015% ◦ Commonly called heavy hydrogen or “deuterium” ◦ Relative abundance = ~0. 00% ◦ Commonly called “tritium”

Atomic Mass = weighted average mass of the atoms in a naturally occurring sample of the element � Definition ◦ Units = amu �Equal to 1/12 the mass of a carbon-12 atom ◦ This is the mass that is on the periodic table ◦ Based on the mass and abundance of each isotope

Atomic Mass � Formula: Atomic mass = Abundance x mass ISOTOPE #1 � + Abundance x mass ISOTOPE #2 Repeats for however many isotopes exist for that element….

Atomic Mass – Sample Problem Atomic mass = Abundance x mass + Abundance x mass Chlorine has 2 isotopes: chlorine-35 has an abundance of 75. 77% and chlorine-37 which is 24. 33% abundant. What is the atomic mass of chlorine? Atomic mass = (35*0. 7577) + (37*0. 2433) Atomic mass = 35. 5 amu

CH 5 EOC Questions � Answer the following in your composition book � Questions found on page 129 � #33, 36, 38 -43, 45 -46, 48 -49, 53, 57