Chapter 5 The Periodic Table

Chapter 5 The Periodic Table

•Section 5.1 Organizing the Elements•Section 5.2 The Modern Periodic Table•Section 5.3 Representative Groups

Section 5.1 Organizing the Elements

• The Search for Order• The placement of elements on the

periodic table reveals the link between the atomic structure of elements and their properties.

Section 5.1 Organizing the Elements• The Search for Order

• As # of known elements grew, the need to organize them did also.

• Antoine Lavoisier (1789), French chemist: grouped known elements into categories: metals, nonmetals, gases, and earths

• Dmitri Mendeleev, Russian chemist/teacher: found a way to organize the elements


• Mendeleev’s Periodic Table: Mendeleev’s Proposal

• Used deck of cards (4 columns); break the elements into rows

• Key Concept: Mendeleev arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column.


• Mendeleev’s Proposal• Periodic table-an arrangement of

elements in columns, based on a set of properties that repeat from row to row

Section 5.1: Organizing the Elements

• Mendeleev’s Prediction• Some elements that had not been

discovered yet, he left spaces for; also predicted the properties for them

Mendeleev’s Table of Elements (1872)

Figure 3


• Evidence Supporting Mendeleev’s Table• Key Concept: The close match between

Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be.


• Evidence Supporting Mendeleev’s Table• With the periodic table, chemists could

do more than predict properties of new elements

• They could explain the chemical behavior of different groups of elements

Section 5.2 The Modern Periodic Table

• The Periodic Law• You can use the modern periodic table

to classify elements and to compare their properties.

• Key Concept: In the modern periodic table, elements are arranged by increasing atomic number (# of protons)

Periodic Table of ElementsFigure 7


• The Periodic Law: Periods• Period-each row in the table of elements• # of elements per period varies b/c # of

orbitals increases from energy level to energy level

• Ex. Period 1 (H and He); Period 2 (Li, Be, B, C, N, O, F, and Ne)


• The Periodic Law: Groups• Group-each column on the periodic

table• Key Concept: Properties of elements

repeat in a predictable way when atomic numbers are used to arrange elements into groups.


• The Periodic Law: Groups• Elements in group have same electron

configuration• **Electron configuration determines

element’s chemical properties• Members of a group have similar

chemical properties• Periodic law-pattern of repeating

properties


• Atomic Mass• Key Concept: Atomic mass is a value

that depends on the distribution of an element’s isotopes in nature and the masses of those isotopes.


• Atomic Mass: Atomic Mass Units• To have a simple way to compare the

masses of atoms, scientists chose 1 isotope to serve as a standard.

• Assigned 12 atomic units to carbon-12 atom (6 protons and 6 neutrons)

• **Atomic mass unit (amu)-one twelfth of a carbon-12 atom


• Atomic Mass: Isotopes of Chlorine and Weighted Averages

• Most elements exist in nature exist as a mix of 2 or more isotopes.

• 2 natural isotopes of chlorine (Chlorine-35 and Chlorine-37); Chlorine 37 has more neutrons (greater mass)

• Atomic mass of 35.453; atomic masses of the isotopes get averaged together

Isotopes of Chlorine

Figure 9

Section 5.2 The Modern Periodic Table• Classes of Elements

• Periodic table- 3 ways to classify elements1. Solids (black), liquids (purple), or gases (red)2. Elements are divided into those that occur

naturally (1-92) and those that don’t (93 and higher)

3. Based on general properties: Key Concept: Elements are classified as metals, nonmetals, and metalloids.



• Classes of Elements: Metals (Blue)• Def.-elements that are good conductors of

electric current and heat.• Majority of elements are metals.• Some extremely reactive, some don’t react

easily• Transition metals (Groups 3-12)-elements that

form a bridge b/t the elements on the left and right sides of the periodic table


• Classes of Elements: Nonmetals (Yellow/Orange)

• Have properties opposite of metals• Def.-elements that are poor conductors

of heat and electric current• Have low boiling points=many are gas

at room temp.


• Classes of Elements: Metalloids (Green)• Def.-elements with properties that fall

between those of metals and nonmetals• Ability to conduct electric current varies

with temperature.


• Variation Across a Period• Key Concept: Across a period (row)

from left to right, the elements become less metallic and more nonmetallic in their properties.

• Most reactive metals-left side• Most reactive nonmetals-right side

Periodic Table of Elements

Figure 7

Section 5.3 Representative Groups

• Valence Electrons• The # of an A group matches the # of

valence electrons in an electron configuration for an element in that group.

• Def.-an electron that is in the highest occupied energy level of an atom


• Valence Electrons• Valence electrons play a key role in chemical

reactions.• **Properties vary across a period (row) b/c the

number of valence electrons increases from left to right.

• Key Concept: Elements in a group have similar properties because they have the same number of valence electrons.



• The Alkali Metals-Group 1A• Li, Na, K, Rb, Cs, Fr• Have one valence electron • Are extremely reactive; found in nature

only as compounds• Key Concept: The reactivity of alkali

metals increases from the top of Group 1A to the bottom.


• The Alkaline Earth Metals-Group 2A• Be, Mg, Ca, Sr, Ba, Ra• Have 2 valence electrons• Harder than Group 1A metals• Key Concept: Differences in reactivity among

the alkaline earth metals are shown by the ways they react with water (ex. Ca, Sr, Ba-cold water) and (Mg-hot water)

• Mg & Ca-essential for biological functions and provide materials used in construction and transportation


• The Boron Family-Group 3A• Have 3 valence electrons• B, Al, Ga, In, Tl• Key Concept: Aluminum is the most

abundant metal in Earth’s crust.• Al-car parts, packaging, airplanes• B-glass that does not shatter easily w/

rapid temp. change (lab glassware)


• The Carbon Family-Group 4A• C, Si, Ge, Sn, Pb• Have 4 valence electrons• Metallic nature of group increases from top to

bottom (conductivity)• Life on Earth would not exist w/o Carbon• Key Concept: Except for water, most of the

compounds in your body contain carbon.• Silicon-the 2nd most abundant element in the

Earth’s crust


• The Nitrogen Family-Group 5A• N, P, As, Sb, Bi• Have 5 valence electrons• Includes elements w/ wide range of

physical properties• N & P-most important• Key Concept: Besides nitrogen,

fertilizers often contain phosphorus.


• The Oxygen Family-Group 6A• O, S, Se, Te, Po• Have 6 valence electrons• Key Concept: Oxygen is the most

abundant element in the Earth’s crust.• Complex forms of life need O to live.• Ex. Oxygen tanks, ozone layer• S-used in fertilizers


• The Halogens-Group 7A• F, Cl, Br, I, At• Have 7 valence electrons• Key Concept: Despite their physical

differences, the halogens have similar chemical properties. Pg. 144

• Highly reactive nonmetals; reactivity decreases from top to bottom (F)

• F-prevents tooth decay, Cl-kills bacteria, and I-thyroid gland function


• The Noble Gases-Group 8A• He, Ne, Ar, Kr, Xe, Rn• He has 2 valence electrons; all other have 8

valence electrons• Key Concept: The noble gases are colorless

and odorless and extremely unreactive.• Ex. Argon-light bulbs; all are used in neon

lights except Radon• He-pink, Ne orange-red, Ar-lavender, Kr-white,

Xe-blue

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Chapter 5 The Periodic Table