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Periodic Table (Ch 2 Gen Chem)

General Chemistry Chapter 2
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Dmitri Mendeleev
Published the first version of his periodic table
Published the first version of periodic table
Dmitri Mendeleev
Periodic table
Showed that ordering the known elements according to atomic weight produced a pattern of periodically recurring physical and chemical properties; revised to be organized by increasing atomic number
Shows that ordering the known elements according to atomic weight produced a pattern of periodically recurring physical and chemical properties?
Periodic table
Who helped revise the periodic table of the elements that was originally created by Dmitri Mendeleev?
Henry Moseley
How did Henry Moseley revise the periodic table?
Organized the elements on the basis of increasing atomic number rather than atomic weight
Periodic law
the chemical and physical properties of the elements are dependent, in a periodic way, upon their atomic numbers
the chemical and physical properties of the elements are dependent, in a periodic way, upon their atomic numbers
Periodic law
How does the modern periodic table arrange the elements?
Periods (rows) and groups (columns) which are also known as families.
How many periods are there?
Seven periods; representing the principal quantum numbers n=1 and n=7.
Each element compared to the one next to it in a period?
Each element in a given period has one more proton and one more electron (in the neutral state) than the element to its left
Groups/families include elements that have what electronic similarity?
Include elements that have the same electronic configuration in their valence shell, which is the outermost shell, and share similar chemical properties
What includes elements have the same electronic configuration in their valence shell, which is the outermost shell, and share similar chemical properties?
Groups/families
What are the electrons in the valence shell known as?
Valence electrons
What electrons in an atom are the furthest from the nucleus and have the greatest amount of potential energy?
Valence electrons
What allows valence electrons to become involved in chemical bonds with other atoms?
Their higher potential energy and the fact that they are held less tightly by the nucleus
Roman numeral classification of groups in the periodic table
The Roman numeral above each group represents the number of valence electrons. The roman numeral is combined with the letter A or B to separate the elements into two larger classes (A are representative elements and B are nonrepresentative elements)
The A elements in the periodic table
Representative elements; Include groups IA, IIA, IIIA, IVA, VA, VIA, VIIA, VIIIA; The elements in these groups have their valence electrons in the orbitals of either s or p subshells
The elements in this groups have their valence electrons in the orbitals of either s or p subshells
The A elements (representative elements)
The B elements in the periodic table
Nonrepresentative elements; Include the transition elements which have valence electrons in the s and d subshells and the lanthanide actinide series which have valence electrons in the s,d, and f subshells; Not required to know identification of electronic configuration based on roman numerals for the nonrepresentative elements
The elements in this group have their valence electron in the orbitals of s and d subshells or the s,d, and f subshells
The B elements (nonrepresentative)
What system has IUPAC developed in place of roman numerals in the periodic table
A group identification system using Arabic numbers, 1-18, starting with the alkali metals on the left and ending with the noble gases on the right
What happens as the positivity of the nucleus increases as you go from left to right across a period
The electrons surrounding the nucleus, including those in the valence shell, experience a stronger electrostatic pull toward it. This causes the electron cloud (the outer boundary which is defined by the valence shell electrons) to move closer and bind more tightly to the nucleus
The electrostatic attraction between the valence shell electrons and nucleus; a measure of the net positive charge experienced by the outermost electrons
Effective nuclear charge (Z_eff)
Effective nuclear charge
Z_eff; The electrostatic attraction between valence shell electrons and nucleus; a measure of the net positive charge experienced by the outermost electrons
Elements in the same period and Z_eff?
Increases from left to right
As you go down the elements of a given group/family what happens to the principal quantum number and valence electrons
The principal quantum number increases by one each time. This means that the valence electrons are increasingly separated from the nucleus by a greater number of filled principal energy levels
Shielding and positivity of nucleus relationship as you go down the periodic table?
Increase in the shielding effect of the additional insulating layer of inner shell electrons negates the increase in the positivity of the nucleus (nuclear charge)
Elements in the same group/family and Z_eff?
Constant among the elements within a given group
How tightly are valence electrons held to the nucleus as you go down a family/group?
held less tightly as you go down a given group due to the increased separation between the valence electrons and nucleus; this holds true even though the effective nuclear charge remains constant down a group
in what general way do elements behave in their gain/loss of electrons?
They behave in such a way as to achieve the stable octet formation possessed by the inert (noble) gases (Group VIII/Group 18); they tend to want to have eight electrons in their valence shell
Is the octet rule truly a rule?
No; a far greater number of elements can be exceptions to this rule than elements that always follow it; However elements tend to want to have eight electrons in their valence shell, especially the ones that have biological roles.
What guiding principles can help you derive all the periodic trends?
The periodic trends for Z_eff; Z_eff increases as you go across a period and essentially remains constant going down a group/family
Atomic radius of an element
Equal to one half the distance between the centers of two atoms of an element that are just touching each other
Equal to one half the distance between the centers of two atoms of an element that are just touching each other
Atomic radius of an element
Why can't we examine the atomic radius using a single atom?
Because the electrons are constantly moving around an it becomes impossible to mark the outer boundary of the electron cloud)
Atomic radius trend across a period
Decreases from left to right across a period
Why does the atomic radius decrease from left to right across a period
As we move across a period protons and electrons are added one at a time; Because the electrons are being added only to the outermost shell, the increasing positive charge of the nucleus holds the outer electrons more closely and more tightly; Z_eff increases left to right across a period
Atomic radius trend down a group/family
Increases from top to bottom
Why does the atomic radius increase from top to bottom in a group/family
As we move down a group, the increasing principal quantum number implies that the valence electrons will be found farther away from the nucleus because the number of inner shells is increasing; Although Z_eff remains constant the radius does not
Where will the largest atom in the periodic table be?
Group 1 at the bottom
Ionization energy
IE; Also known as ionization potential, is the energy required to remove an electron completely from a gaseous atom or ion
The energy required to remove an electron completely from a gaseous atom or ion
Ionization energy (IE); also known as ionization potential
Ionization energy is what type of thermodynamic process?
Removing an electron from an atom always requires an input of energy (endothermic)
Ionization energy trend?
Increases from left to right across a period and decreases in a group from top to bottom
Explain the ionization energy trend?
The higher the atom's Z_eff or the closer the valence electrons are to the nucleus, the more tightly they are bound to the atom making it more difficult to remove one or more electrons.
Energy of taking out second or third electrons after first ionization energy?
The subsequent removal of a second or third electron requires increasing amounts of energy because the removal of more than one electron necessarily means that the electrons are being removed from an increasingly cationic species
The energy necessary to remove the first electron
First ionization energy
First ionization energy
The energy necessary to remove the first electron
The energy necessary to remove the second electron from the univalent cation to form the divalent cation
Second ionization energy
Second ionization energy
The energy necessary to remove the second electron from the univalent cation to form the divalent cation
What elements have relatively low ionization energies?
Elements in Groups 1 and 2 (active metals); Active metals never exist naturally in their neutral elemental (native) forms; they are always found in ionic compounds, minerals, or ores
Ionization energy of the active metals
Relatively low
What results in the formation of a stable, filled valence shell for active metals?
The loss of one electron from the alkali metals or the loss of two electrons from the alkaline earth metals
What elements have very large ionization energies?
Group 17 (the halogens) and Group 18 (noble gases)
Ionization energy of Group 17/18?
Very high
Willingness for halogens to give up electrons?
Very unwilling; in their monatomic ion form, they are found only as anions.
Size of halogen atom and ionization energy?
Halogens have large ionization energies; The smaller the halogen atom the higher the ionization energy
What is the only group less willing to give up their valence electrons than halogens?
The inert elements (noble gases); They already have a very stable electron configuration and are unwilling to disrupt that stability by losing an electron. Inert gases are among the elements with the highest ionization energies.
Electron affinity
A release of energy when an atom gains electrons
A release of energy when an atom gains electrons
Electron affinity
Thermodynamics of electron affinity
Exothermic
What type of value is electron affinity reported as?
A positive energy value, even though by the conventions of thermodynamics, exothermic processes have negative energy changes
Cesium (Cs) and how it can help you remember periodic trends
Cesium is the largest, most metallic, and least electronegative of all naturally occurring elements. It also has the smallest ionization energy and the least exothermic electron affinity
Fluorine (F) and how it can help you remember periodic trends
Fluorine is the smallest, most electronegative element. It also has the largest ionization energy and most exothermic electron affinity
Explain the trends for electron affinity?
The stronger the electrostatic pull (Z_eff) between the nucleus and the valence electrons the greater the energy release will be when the atom gains the electron; closeness of the valence shell to the nucleus
Trends for electron affinity
Electron affinity increases across a period from left to right; decreases in a group from top to bottom
Groups 1 and 2 electron affinities
Very low; prefer to give up one or two electrons to achieve the octet configuration of the prior noble gas
What elements have very low electron affinities?
Groups 1 and 2
Group 17 electron affinity
Very high because they need to gain only one electron to achieve the octet configuration of the immediately following noble gases in Group 18
What elements have very high electron affinities?
Group 17
Group 18 electron affinities
Although the noble gases are the group of elements farthest to the right and would be predicted to have the highest electron affinities according to the trend, they actually have electron affinities to the order of zero since they already possess a stable octet and cannot readily accept an electron.
Electronegativity
A measure of the attractive force that an atom will exert on an electron in a chemical bond.
A measure of the attractive force that an atom will exert on an electron in a chemical bond
Electronegativity
How is electronegativity related to ionization energy?
The lower the IE the lower the eN; the higher the IE the higher the eN
Most common scale for electronegativity?
Pauling electronegativity scale (0.7 for cesium and 4 for fluorine)
Electronegativity trend
Increases across a period from left to right and decreases in a group from top to bottom
All the important periodic trends
Atomic radius is the opposite of all the other trends

L-->R
Atomic radius (down), IE (up), electron affinity (up), eN (up)

T-->B
Atomic radius (up), IE (down), electron affinity (down), eN (down)
What are the three main types of elements?
Metals, nonmetals, metalloids
Metals, nonmetals, metalloids
After considering trends of chemical reactivity and physical properties these three groups of elements exist
Where are metals found in the periodic table?
Both on the left side and in the middle of the periodic table; These include the active metals, the transition metals, and the lanthanide and actinide series of elements
What state are metals often found under standard state conditions?
Shiny solids except for mercury, which is a liquid under standard state conditions
Metal melting point
Generally high
Metal density
Generally high; exceptions to this include lithium which has a density about half that of water
The ability of metal to be hammered into shapes
Malleability
Malleability
the ability of metal to be hammered into shapes
Ductility
The ability to be drawn into wires
The ability to be drawn into wires
Ductility
Z_eff, eN, atomic radius, and ionization energy of metals?
Low Z_eff, low eN, large atomic radius, and low ionization energy defines metals
What does a low Z_eff, low eN, large atomic radius, and low ionization energy make it easy for metals to do?
Give up one or more electrons
Oxidation states of transition metals
Known to have two or more oxidation states
Conductivity of metals
Because the valence electrons of all metals are only loosely held to their atoms, they are essentially free to move, which makes metals generally good conductors of heat and electricity
Where are the valence electrons of metals found?
Active metals (s subshell); Transition metals (d subshell) lanthanide and actinide (f subshell)
What metals are good for coins and jewelry
Some transition metals such as copper, nickel, silver, gold, palladium, and platinum-which are relatively nonreactive
Where are nonmetals found on the periodic table?
Upper right side of the periodic table
State of nonmetals under standard state conditions?
Generally brittle in the solid state and show little or no metallic luster
IE, electron affinities, eN, atomic radius of nonmetals
High IE, electron affinity, eN, small atomic radius
Nonmetals as conductors?
Generally poor conductors of heat and electricity
Nonmetal vs metal unification in properties
Nonmetals are less unified in their chemical and physical properties than are the metals
How are nonmetals and metals separated on the periodic table?
A diagonal band of elements called the metalloids
What are metalloids also known as?
Semimetals because they possess characteristics that are between those of metals and nonmetals
eN and IE of metalloids
Lie between those of metals and nonmetals
Physical properties of metalloids
(density, mp, bp) vary widely and can be combinations of metallic and nonmetallic characteristics
Example of silicon as a metalloid and its physical properties
Has a metallic luster but is brittle and a poor conductor
Reactivity of metalloids
Dependent upon the elements with which they are reacting. Boron reacts as a nonmetal when reacting with sodium (Na) but as a metal when reacting with fluorine (F).
What elements are metalloids
Boron, silicon, germanium, arsenic, antimony, tellurium, and polonium
Alakli metal physical properties
Possess most of the classic physical properties of metals, except that their densities are lower than those of other metals
Alkali metal electrons, Z_eff, atomic radii, IE, electron affinity, eN
Alkali metals have only one loosely bound electron in their outermost shells, and the Z_eff values are very low, giving them the largest atomic radii of all the elements in their respective periods. The very low Z_eff values also result in low ionization energies, low electron affinities, and low eN, and these atoms easily lose one electron to form univalent cations
What do alkali metals react with?
React very readily with nonmetals, especially halogens
Alkaline earth metal characteristics of metals (vs. alkali metals)
Possess many properties characteristic of metals. They share most of the characteristics of the alkali metals except that they have slightly higher effectiven uclear charges and so have slightly smaller atomic radii
Electrons in alkaline earth metals
Have two electrons in their valence shell, both of which are easily removed to form divalent cations
Why are the alkali and alkaline earth metals called active metals?
Because they are so reactive that they are not naturally found in their elemental (neutral) state
Halogen reactivity and number of electrons
Highly reactive nonmetals with seven valence electrons
Halogen physical properties
Highly variable; for example the halogens range from gaseous (F2 and Cl2) to liquid (Br2) to solid (I2) at room temperature
Halogen chemical reactivity uniformity
More uniform than physical properties, due to their very high eN and electron affinities they are especially reactive toward the alkali and alkaline earth metals
What element has the highest electronegativity?
Fluorine
Fluorine electronegativity?
Highest among the elements
How are halogens naturally found?
The halogens are so reactive that they are not naturally found in their elemental state but rather as ions (called halides).
What are noble gases also known as?
Inert gases because they have very low chemical reactivities as a result of their filled valence shells
Noble gas IE, ability to gain or lose electrons, eN
Very high IE, no tendency to gain/lose electrons, no real eN
Noble gas bp
Low boiling points
Noble gas state at standard conditions
Exist as gases at room temperature
Transition elements electron affinity, IE, and eN
Considered metals and such have low electron affinities, low ionization energies, and low electronegativities
Transition metal hardness mp and bp
Hard and have high mp and bp
Malleability and conductivity of transition metals?
Tend to be quite malleable and are good conductors due to the loosely held electrons that are progressively filling the d subshell orbitals in the valence shell
Unique property of transition metals
Many of them can have different possible charged forms or oxidation states because they are capable of losing various numbers of electrons from the s and d orbitals of the valence shell
What does multiple oxidation states cause in transition metals
Because of this ability to attain different positive oxidation states, transition metals form many different ionic and partially ionic compounds. The dissolved ions can form complex ions either with molecules of water (hydration complexes) or with nonmetals, forming highly colored solutions and compounds
Complexation of transition metals may enhance what?
Relatively low solubility of certain compounds. Ex: AgCl is insoluble in water but quite soluble in aqueous ammonia due to the formation of the complex ion [Ag(NH3)2^+]
Formation of complexes causes what to happen in orbitals?
The formation of complexes causes the d orbitals to split into two energy sublevels. This enables many of the complexes to absorb certain frequencies of light-those containing the precise amount of energy required to raise electrons from the lower to the higher d sublevel; Frequencies not absorbed (subtraction frequencies) give complexes their characteristic colors
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