Chapter 4 The Periodic Table. Chapter 4 – The Periodic Table Section 1 - How Are Elements Organized? Pure elements at room temperature and atmospheric

Chapter 4 The Periodic Table

Chapter 4 – The Periodic TableSection 1 - How Are Elements Organized?

Pure elements at room temperature and atmospheric pressure can besolids, liquids, or gases. Some elements are colorless. Others are colored. Despite the differences between elements, groups of elements share certain properties.

Similarly, the elements fluorine, chlorine, bromine, and iodine cancombine with sodium in a 1:1 ratio to form NaF, NaCl, NaBr, and NaI.These compounds are also white solids that can dissolve in water to formsolutions that conduct electricity. These examples show that even thougheach element is different, groups of them have much in common.


In 1865, the English chemist John Newlands arranged the known elements according to their properties and in order of increasing atomic mass. He placed the elements in a table.

In 1869, the Russian chemist Dmitri Mendeleev used Newlands’s observationand other information to produce the first orderly arrangement, orperiodic table, of all 63 elements known at the time. Mendeleev arranged the elements in order of increasing atomic mass. Mendeleev started a new row each time he noticed that the chemical properties of the elements repeated.


He placed elements in the new row directly below elements of similar chemical properties in the preceding row. He arrived at the pattern shown below.

Two interesting observations can be made about Mendeleev’s table.First, Mendeleev’s table contains gaps that elements with particular

properties should fill. He predicted the properties of the missing elements.


Second, the elements do not always fit neatly in order of atomic mass.For example, Mendeleev had to switch the order of tellurium, Te, andiodine, I, to keep similar elements in the same column. At first, he thoughtthat their atomic masses were wrong. However, careful research by othersshowed that they were correct. Mendeleev could not explain why hisorder was not always the same.

About 40 years after Mendeleev published his periodic table, an Englishchemist named Henry Moseley found a different physical basis for thearrangement of elements. Moseley realized that the periodic table should be arranged by atomic number, not atomic mass. When the elements were arranged by increasing atomic number, the discrepancies in Mendeleev’s table disappeared.


The periodic law states that the repeating physical and chemical properties of elements change periodically with their atomic number

To understand why elements with similar properties appear at regularintervals in the periodic table, you need to examine the electron configurationsof the elements.

Elements in each column of the table have the same number of electrons in their outer energy level. These electrons are called valence electrons.

A vertical column on the periodic table is called a group or family.

A horizontal row on the periodic table is called a period.

Chapter 4 – The Periodic TableSection 2 - Tour of the Periodic Table

Elements in groups 1, 2, and 13–18 are known as the main group elements.

Four groups within the main-group elements have special names.These groups are the alkali metals (Group 1), the alkaline-earth metals(Group 2), the halogens (Group 17), and the noble gases (Group 18).


The Alkali Metals Make Up Group 1

Alkali metals are so named because they are metals that react with water to make alkaline solutions.

All have a single valence electron

Alkali metals are usually stored in oil to keep them from reacting withthe oxygen and water in the air. Because of their high reactivity, Alkali metals are never found in nature as pure elements but are found combined with other elements as compounds.


The Alkaline-Earth Metals Make Up Group 2

Like the alkali metals, the alkaline-earth metals are highly reactive, so they are usually found as compounds rather than as pure elements

All have 2 valence electrons

The alkaline-earth metals are not as reactive as alkali metals, however they are harder and have higher melting points.


The Halogens make up Group 17

Halogens have 7 valence electrons

The halogens are the most reactive groupof nonmetal elements

The halogens have a wide range of physical properties. Fluorine andchlorine are gases at room temperature, but bromine, is a liquid, and iodine and astatine are solids.


The Noble Gases make up Group 18

The noble gases were once called inert gases because they werethought to be completely unreactive.

The low reactivity of noble gases leads to some special uses. Helium, a noble gas, is used to fill blimps because it has a low density and is not flammable.

Hydrogen Is in a Class by ItselfHydrogen is the most common element in the universe. It is estimated thatabout three out of every four atoms in the universe are hydrogen. Becauseit consists of just one proton and one electron, hydrogen behaves unlike anyother element.


The Transition metals make up Groups 3 through 12 Unlike the main-group elements, the transitionmetals in each group do not have identical outer electron configurations. Generally, the transition metals are less reactive than the alkali metals and the alkaline-earth metals are.

Lanthanides and Actinides Part of the last two periods of transition metals are placed toward the bottom of the periodic table to keep the table conveniently narrow, The elements in the first of these rows are called the Lanthanides because their atomic numbers follow the element lanthanum.

Likewise, elements in the row below the lanthanides are calledActinides because they follow actinium.


Summary of properties of selected groups

Group 1 – All have 1 valence electron, and will easily lose this electronto form 1+ ions

Group 2 – All have 2 valence electrons, and will easily lose both electronsto form 2+ ions

Group 13 – All have 3 valence electrons, and will easily lose all of them to Form 3+ ions

Group 16 – all have 6 valence electrons and will easily gain 2 electron to Form 2- ions

Group 17 – all have 7 valence electrons and will easily gain 1 electron to Form 1- ions

Group 18 – have a full outer shell with 8 electrons and will not react with other atom easily.


Transition elements – are able to have multiple ion charges. All Possible charges are positive due to lose of electrons. Many will form a colored aqueous solution.


Most elements of the periodic table are called Metals

All metals are excellent conductors of electricity.

Metals are excellent conductors of heat.

Metals are ductile and malleable.

Ductile means that the metal can be squeezed out into a wire.

Malleable means that the metal can be hammered orrolled into sheets.

Metals tend to lose electrons to complete the octet rule.

All metals are solid except mercury, which is a liquid.


Most elements of the periodic table near groups 14 -18 are called Nonmetals

All nonmetals are poor conductors of electricity.

Metals are poor conductors of heat.

Solid nonmetals are brittle and break easily

Metals tend to gain electrons to complete the octet rule.

Nonmetals are found in all three states of matter with bromine being the onlyliquid.

Metalloids are elements that share properties of both metals and nonmetals

Metalloids are elements B, Si, As, Te, At, Ge, Sb and Po


Review Questions

At STP which element has a definite shape and volume?1. Ag 2. Hg 3. Ne 4. Xe

Which element is a member of the halogen family?1. K 2. B 3. I 4. S


Review QuestionsThe metalloids that are included in Group 15 are antimony (Sb) and1. N 2. P 3. As 4. Bi

A characteristic of most nonmetallic solids is that they are1. brittle 2. ductile 3. malleable 4. conductors of electricity

More than two-thirds of the elements of the Periodic Table are classified as1. metalloids 2. metals 3. nonmetals 4. noble gases


Review QuestionsTo which group do the alkaline earth metals belong?1. 1 2. 23. 114. 12

Which three elements have the most similar chemical properties?1. Ar, Kr, Br 2. K, Rb, Cs 3. B, C, N 4. O, N, SiWhen metals form ions, they tend to do so by1. losing electrons and forming positive ions 2. losing electrons and forming negative ions 3. gaining electrons and forming positive ions 4. gaining electrons and forming negative ions


Review Questions

The chemical properties of the elements are periodic functions of their atomic1. masses 2. weights 3. numbers 4. radii

Which halogen is a solid at STP?1. fluorine 2. chlorine 3. bromine 4. iodine

Which element is in Group 2 and Period 7 of the Periodic Table?1. magnesium 2. manganese 3. radium 4. radon


Review QuestionsAn atom in the ground state contains 8 valence electrons. This atom is classified as a1. metal 2. semimetal 3. noble gas 4. halogen

Which category is composed of elements that have both positive and negative charges? 1. the alkali metals 2. the transition metals 3. the halogens 4. the alkaline earths


Review QuestionsWhich element is so active chemically that it occurs naturally only in compounds?1. potassium 2. silver 3. copper 4. sulfur

The elements of the Periodic Table are arranged in horizontal rows according to each successive element's greater1. atomic mass 2. atomic radius 3. number of protons 4. number of neutrons


Review QuestionsIn which list are the elements arranged in order of increasing atomic mass?1. Cl, K, Ar 2. Fe, Co, Ni 3. Te, I, Xe 4. Ne, F, Na

Which Group of the Periodic Table contains atoms with a stable outer electron configuration?1. 1 2. 8 3. 16 4. 18The element in Period 4 and Group 1 of the Periodic Table would be classified as a1. metal 2. metalloid 3. nonmetal 4. noble gas

Chapter 4 – The Periodic TableSection 3 - Trends in the Periodic Table

The arrangement of the periodic table reveals trends in the properties ofthe elements. A trend is a predictable change in a particular direction.

Metallic TrendAll of the elements of the periodic table increase in metalliccharacteristics as they get closer to francium.

This will make group 1 the most metallic group and period 7 themost metallic period.

Nonmetallic TrendAll of the elements of the periodic table increase in nonmetalliccharacteristics as they get closer to flourine.This will make group 17 the most nonmetallic group and period 2 themost nonmetallic period.

Note: The noble gases are not considered part of the metallic or nonmetallic trendsdue to there resistance to chemical reactions.


Ionization Energy

The energy that is supplied to remove an electron is the ionization energyof the atom.


Ionization Energy Decreases as You Move Down a Group

Each element has more occupied energy levels than the one above it has. Therefore, the outermost electrons are farthest from the nucleus in elements near the bottom of a group.

Similarly, as you move down a group, each successive element containsmore electrons in the energy levels between the nucleus and theoutermost electrons. These inner electrons shield the outermost electronsfrom the full attractive force of the nucleus. This electron shielding causesthe outermost electrons to be held less tightly to the nucleus.


Ionization Energy Increases as You Move Across a Period

From one element to the next in a period, the number of protons and the number of electrons increase by one each. A higher nuclear charge more strongly attracts the outer electrons in the same energy level, but the electron-shielding effect from inner-level electrons remains the same. Thus, more energy is required to remove an electron because the attractive force on them is higher.



Atomic RadiusThe exact size of an atom is hard to determine. An atom’s size depends onthe volume occupied by the electrons around the nucleus, and the electronsdo not move in well-defined paths. Rather, the volume the electronsoccupy is thought of as an electron cloud, with no clear-cut edge. In addition,the physical and chemical state of an atom can change the size of anelectron cloud.The diagram below shows one way to measure the size of an atom. This Method involves calculating the bond radius, the length that is half the distancebetween the nuclei of two bonded atoms. The bond radius can changeslightly depending on what atoms are involved.


Atomic Radius Increases as You Move Down a GroupAs you proceed from one element down to the next in a group, anotherprincipal energy level is filled. The addition of another level of electronsincreases the size, or atomic radius, of an atom.

Atomic Radius Decreases as You Move Across a PeriodAs you move from left to right across a period, each atom has one moreproton and one more electron than the atom before it has. As a result, electron shielding does not play a role as you move across a period. Therefore, as the nuclear charge increases across a period, the effective nuclear charge acting on the outer electrons also increases. This increasing nuclear charge pulls the outermost electrons closer and closer to the nucleus and thus reduces the size of the atom.



Electronegativity Atoms often bond to one another to form a compound. These bonds caninvolve the sharing of valence electrons. Not all atoms in a compoundshare electrons equally. Knowing how strongly each atom attracts bondingelectrons can help explain the physical and chemical properties of thecompound. Linus Pauling, one of America’s most famous chemists, made a scaleof numerical values that reflect how much an atom in a molecule attractselectrons, called electronegativity values. Chemical bonding that comesfrom a sharing of electrons can be thought of as a tug of war. The atomwith the higher electronegativity will pull on the electrons more stronglythan the other atom will. Fluorine is the element whose atoms most strongly attract sharedelectrons in a compound. Pauling arbitrarily gave fluorine an electronegativityvalue of 4.0.Values for the other elements were calculated in relationto this value.


Electronegativity Decreases as You Move Down a Group

Metals tend to have small electronegativity because they would rather lose an electron than gain electrons to fulfill the octet rule.

As you go down a group the distance between the valence electrons andthe nucleus increase, weakening the “grip” the nucleus has on it valence electrons due to electron shielding.

Electronegativity Increases as You Move Across a PeriodNonmetals tend to have large electronegativity because they would rather gain an electron than lose electrons to fulfill the octet rule.

As you go across a period the distance between the valence electrons andthe nucleus decreases, strengthening the “grip” the nucleus has on it valence electrons.



Periodic Trends in Ionic Size Recall that atoms form ions by either losing or gaining electrons. Likeatomic size, ionic size has periodic trends. As you proceed down a group,the outermost electrons in ions are in higher energy levels. Therefore, justas atomic radius increases as you move down a group, usually the ionicradius increases as well. These trends hold for both positive and negative ions. Metals tend to lose one or more electrons and form a positive ion. Asyou move across a period, the ionic radii of metal cations tend to decreasebecause of the increasing nuclear charge. As you come to the nonmetalelements in a period, their atoms tend to gain electrons and form negativeions. The diagram on the next slide shows that as you proceed through the anions on the right of a period, ionic radii still tend to decrease because of the anions’ increasing nuclear charge.


Summary of Ionic Radii

Atoms that form anions will increase in ionic radius, due to the nuclear charge becoming less than the total electron cloud charge.Atoms that form cations will decrease in ionic radius due to the nuclearcharge becoming greater than the electron cloud charge.

All atoms forming anions or cations will increase ionic radius whenmoving down a group because of the addition of a principle energylevel.


Other information about the periodic table.

All elements with an atomic number greater than 83 have isotopes that are not stable and will undergo nuclear decay. (They are radioactive)

Chemistry Reference tables lists, electronegativity and ionizations energiesand atomic radii.


Which element forms an ion that is larger than its atom?1. Cl 2. Ca 3. Li 4. MgWhich atom has a radius larger than the radius of its ion?1. Cl 2. Ca 3. S 4. SeWhich of the following elements in Period 3 has the greatest metallic character?1. Ar 2. Si 3. Mg 4. S


Which period of the Periodic Table contains more metallic elements than nonmetallic elements?1. Period 1 2. Period 2 3. Period 3 4. Period 4As the elements in Period 3 are considered from left to right, they tend to1. lose electrons more readily and increase in metallic character 2. lose electrons more readily and increase in nonmetallic character 3. gain electrons more readily and increase in metallic character 4. gain electrons more readily and increase in nonmetallic character

Compared to the nonmetals in Period 2, the metals in Period 2 generally have larger1. ionization energies 2. electronegativities 3. atomic radii 4. atomic numbers


Which of the following Group 2 elements has the lowest first ionization energy?1. Be 2. Mg 3. Ca 4. Ba

Which of the following atoms has the greatest tendency to attract electrons?1. barium 2. beryllium 3. boron 4. bromine

In which shell are the valence electrons of the elements in Period 2 found? 1. 1 2. 2 3. 3 4. 4


Which of the following ions has the smallest radius?1. F- 2. Cl- 3. K+ 4. Ca2+

The ability of carbon to attract electrons is1. greater than that of nitrogen, but less than that of oxygen 2. less than that of nitrogen, but greater than that of oxygen 3. greater than that of nitrogen and oxygen 4. less than that of nitrogen and oxygen

Which trends appear as the elements in Period 3 are considered from left to right?1. Metallic character decreases, and electronegativity decreases. 2. Metallic character decreases, and electronegativity increases. 3. Metallic character increases, and electronegativity decreases. 4. Metallic character increases, and electronegativity increases.


As the atoms in Period 3 of the Periodic Table are considered from left to right, the atoms generally show1. an increase in radius and an increase in ionization energy 2. an increase in radius and a decrease in ionization energy 3. a decrease in radius and an increase in ionization energy 4. a decrease in radius and a decrease in ionization energy

Which Group 16 element has only unstable isotopes?1. Po 2. Te 3. Se 4. SHow much energy is required to remove the most loosely bound electron from a neutral atom of carbon in the gaseous phase? 1. 801 kJ/mol 2. 1086 kJ/mol 3. 1251 kJ/mol 4. 1000 kJ/mol


THE END

ReviewHow is periodic table arranged:In order of atomic number not mass as the

original periodic tables were.

Define:Groups

Periods

Alkali Metals

Alkaline Earth Metals

Halogens

Noble Gases

Go up and down on periodic table

Go across the periodic table

Group 1

Group 2

Group 17

Group 18

Transition Elements Groups 3-12

Metals NonmetalsLocation

Conduct Electricity

Conduct Heat

Malleable

Brittle (if solid)

Tend to ____ Electrons

Name the liquid

Best represents

Left Right

Yes No

Yes No

Yes

Yes

NoNo

Lose Gain

Mercury Bromine

Francium Fluorine

Ionization EnergyEnergy required to remove one valence electron

Electronegativity Willingness to gain an electron

Atomic Radii Size of an atom

Ionic RadiiSize of an atom after it has gained/lost an electron(s)

Group Trend Period Trend

Ionization Energy

Electroneg-ativity

Atomic Radii

Ionic Radii

Decrease due to increase in principle energy levels

Increase due to increase in nuclear charge

Decrease due to larger radiiIncrease due to increase in nuclear charge

Increase due to increase in principle energy levels

Decrease due to increase in nuclear charge

Increase due to increase in principle energy levels. Does not matter if gaining or losing electrons

Varies- If gaining electronsit will increase if losing electrons it will decrease

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Chapter 4 The Periodic Table. Chapter 4 – The Periodic Table Section 1 - How Are Elements Organized? Pure elements at room temperature and atmospheric