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# The periodic table and periodic law chapter 6

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Explain how Mendeleev’s periodic table was in error how was this error fixed?
Mendeleev’s periodic table was in error because when the elements were arranged by mass it resulted in several elements being placed in groups of elements with differing properties.
Explain the contribution of Newland’s law of octaves to the development of the modern periodic table?
Newland’s law of octaves stated that elements properties repeated every eighth element. While this was not completely correct it did lead to the idea of a periodic pattern in the properties of elements.
German chemist Lothar Meyer and Russian chemist Dmitri Mendeleev both propose similar periodic tables in 1869. Why is Mendeleev generally given credit for the periodic table?
Mendeleev is given more credit because he published his organizational scheme and went on to demonstrate its usefulness. Mendeleev predicted the existence of properties of undiscovered elements and left blanks in his periodic table for them.
How was Mendeleev’s periodic table organized?
Mendeleev arrange the elements in order of increasing atomic mass in the columns with similar properties.
What is the periodic law?
The statement that there is a periodic repetition of chemical and physical properties of elements when they arranged by increasing atomic number.
Identify each of the following as a metal nonmetal are metalloid. Oxygen. Barium. Geranium. Iron. Neon. Praseodymium.
Oxygen – nonmetal, barium- metal, germanium – metalloid, Iron – metal, neon – nonmetal, and praseodymium-metal
Describe the general characteristics of metal
Metals are elements that are generally shiny went smooth and clean solid at room temperature and good conductors of heat and electricity most metals also are malleable or ductile.
What group are each of these items Alkali metals, halogens, alkaline earth metals, noble gases.
Alkali – group 1a, halogens- Group 7a, alkaline earth metals -Group 2a, noble gases – Group 8A
Identified these elements as representative elements or transition element oxygen, barium, germanium, iron, neon, and praseodymium.
oxygen-representative, barium-representative, germanium-representative, iron-transition, neon-representative, and praseodymium-transition.
A shiny solid element also is ductile. What side of the periodic table is it likely to be found?
left
What are the general properties of a metalloid? List three metalloid element?
Metalloids are elements with physical and chemical properties of both metals and nonmetals. Boron, geranium, and silicon
What is the purpose of the heavy stairstep to line on the periodic table?
To separate the metals and nonmetals
Describe the two types of numbering used to identify groups on the periodic table?
One type of numbering to use is groups are numbered one through eight followed by the letter a or B. Another more recent membrane system uses numbers one through 18 above each for group.
Give the name and symbol for the two elements that are liquid at room temperature.
Bromine – Br, Mercury – Hg
Give the name and symbol for the noble gas with the greatest atomic mass?
Give the name and symbol of an inner transition metals.
Uranium – U
Why didn’t elements chlorine and Ioline have similar chemical properties?
They are in the same group
How are the numbers of valence electrons of the group a elements related to the group number?
The group number is the number valence electrons in the element.
How is the energy level of an atoms valence electrons related to the period it is in on the periodic table?
The energy level of an element Boelens electrons indicates the period on the periodic table in which it is found?
How many valence electrons do each of the noble gases have
Eight except for helium which has two
What are the four blocks of the periodic table.
S – block, P – block, D -block, F – block
In general, what electronic configuration has the greatest stability?
P⁶, which is the end of the configuration of most of the noble gases
Explain how atoms valence electron configuration determines its place on the periodic table?
It is the group number, and the valence electrons energy level is what period the atom is on.
Explain why the radius of an atom cannot be measured directly?
The radius of the atom is cannot be measured directly because it does not have a definite edge to the electrons cloud
Given any two elements within a group, is the element with a larger atomic number likely to have a larger or smaller atomic radius than the other element?
As you go down the groups the atomic number increases but the size of the atom increases. As you go right through the periods the atomic number goes up but the size of the atom decreases.
Which elements are characterized as having their D orbitals filled with electrons as you move left to right across a period?
Transition metals
Explain why it is harder to remove an inner shell electron then a valence electron from an atom?
It is harder because Adams hold onto their inner core electrons much more strongly than they hold onto their valence electrons. A much larger ionization energy is needed for those inner core electrons.
An element forms a negative ion when ionized. On what side of the periodic table is the element located? Explain?
right. groups one a through four a are positively charged ions with the larger positively charged ions on the left and gradually decreasing as you move right when you get to 5a you’re at the very large negative ions and then they gradually decrease as you move right.
Of the elements magnesium, calcium, barium, which forms the ion with the largest radius? The smallest radius? What periodic trend explains this?
barium, magnesium, as you move down a group, an ion’s outershell are in higher principal energy levels, resulting in a gradual increase in ionic size.
What is iodization energy?
The energy required to remove an electron from a gaseous atom.
Explain why each successive ionization of an electron requires a greater amount of energy?
Each successive ionization of an electron requires a greater amount of energy because as you go inward the electrons closer to the nucleus have a larger pull on them
Which group has the highest ionization energies?
8
Define an ion?
an atom with a charge
How does that ionic radius of a nonmetal compare with its atomic radius? Explain why the changes and radius occur.
The ionic radius of nonmetals increase compared to the atomic radius, because when an atom becomes a negative ion it gains an electron and the size of the radius increases.
Explain why atomic radii decrease as you move left to right across a period.
As you move across the periods from left to right the atomic radii decrease because none of the electrons come between the valence electrons and the nucleus the valence electrons are not shielded from the increased nuclear charge and the result is they are pulled towards the nucleus.
Explain the octet rule.
The octet rule states that atoms tend to gain, lose, or share electrons in order to acquire a full set of eight valence electrons.
How many valence electrons do elements in the following groups have. Group 8A. Group 3A. Group 1A.
8, 3, 1
Na⁺ and Mg²⁺ ions each have 10 electrons surrounding their nuclei which ion would you expect to have the larger radius? why
Na⁺, it has a smaller positive charge so its radius is
What is electronegativity?
The relative ability of an element’s atoms to attract electrons in a chemical bond
How does electronegativity change within the periodic table?
Electronegativity decreases as you move down a group and increases as you move to the right.
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Chapter 6 Q and A

# The Periodic Law

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• Page ID
621
• The periodic law was developed independently by Dmitri Mendeleev and Lothar Meyer in 1869. Mendeleev created the first periodic table and was shortly followed by Meyer. They both arranged the elements by their mass and proposed that certain properties periodically reoccur. Meyer formed his periodic law based on the atomic volume or molar volume, which is the atomic mass divided by the density in solid form. Mendeleev’s table is noteworthy because it exhibits mostly accurate values for atomic mass and it also contains blank spaces for unknown elements.

### Introduction

In 1804 physicist John Dalton advanced the atomic theory of matter, helping scientists determine the mass of the known elements. Around the same time, two chemists Sir Humphry Davy and Michael Faraday developed electrochemistry which aided in the discovery of new elements. By 1829, chemist Johann Wolfgang Doberiner observed that certain elements with similar properties occur in group of three such as; chlorine, bromine, iodine; calcium, strontium, and barium; sulfur, selenium, tellurium; iron, cobalt, manganese. However, at the time of this discovery too few elements had been discovered and there was confusion between molecular weight and atomic weights; therefore, chemists never really understood the significance of Doberiner’s triad.

In 1859 two physicists Robert Willhem Bunsen and Gustav Robert Kirchoff discovered spectroscopy which allowed for discovery of many new elements. This gave scientists the tools to reveal the relationships between elements. Thus in 1864, chemist John A. R Newland arranged the elements in increasing of atomic weights. Explaining that a given set of properties reoccurs every eight place, he named it the law of Octaves.

### The Periodic Law

In 1869, Dmitri Mendeleev and Lothar Meyer individually came up with their own periodic law "when the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically." Meyer based his laws on the atomic volume (the atomic mass of an element divided by the density of its solid form), this property is called Molar volume.

$\textAtomic (molar) volume (cm^3\text/mol) = \dfrac\text molar mass (g/ mol)\rho \text (cm^3\text/g)$

### Mendeleev’s Periodic Table

Mendeleev’s periodic table is an arrangement of the elements that group similar elements together. He left blank spaces for the undiscovered elements (atomic masses, element: 44, scandium; 68, gallium; 72, germanium; & 100, technetium) so that certain elements can be grouped together. However, Mendeleev had not predicted the noble gases, so no spots were left for them.

Figure 1: Mendeleev’s original periodic table4

In Mendeleev’s table, elements with similar characteristics fall in vertical columns, called groups. Molar volume increases from top to bottom of a group3

Example

The alkali metals (Mendeleev’s group I) have high molar volumes and they also have low melting points which decrease in the order:

Li (174 oC) > Na (97.8 oC) > K (63.7 oC) > Rb (38.9 oC) > Cs (28.5 oC)

### Atomic Number as the Basis for the Periodic Law

Assuming there were errors in atomic masses, Mendeleev placed certain elements not in order of increasing atomic mass so that they could fit into the proper groups (similar elements have similar properties) of his periodic table. An example of this was with argon (atomic mass 39.9), which was put in front of potassium (atomic mass 39.1). Elements were placed into groups that expressed similar chemical behavior.

In 1913 Henry G.J. Moseley did researched the X-Ray spectra of the elements and suggested that the energies of electron orbitals depend on the nuclear charge and the nuclear charges of atoms in the target, which is also known as anode, dictate the frequencies of emitted X-Rays. Moseley was able to tie the X-Ray frequencies to numbers equal to the nuclear charges, therefore showing the placement of the elements in Mendeleev’s periodic table. The equation he used:

$\nu = A(Z-b)^2$

with

• $$\nu$$: X-Ray frequency
• $$Z$$: Atomic Number
• $$A$$ and $$b$$: constants

With Moseley’s contribution the Periodic Law can be restated:

Similar properties recur periodically when elements are arranged according to increasing atomic number."

Atomic numbers, not weights, determine the factor of chemical properties. As mentioned before, argon weights more than potassium (39.9 vs. 39.1, respectively), yet argon is in front of potassium. Thus, we can see that elements are arranged based on their atomic number. The periodic law is found to help determine many patterns of many different properties of elements; melting and boiling points, densities, electrical conductivity, reactivity, acidic, basic, valance, polarity, and solubility.

The table below shows that elements increase from left to right accordingly to their atomic number. The vertical columns have similar properties within their group for example Lithium is similar to sodium, beryllium is similar to magnesium, and so on.

Group12131415161718
ElementLiBeBCNOFNe
Atomic Number345678910
Atomic Mass6.949.0110.8112.0114.0115.9918.9920.18
ElementNaMgAlSiPSClAr
Atomic Number1112131415161718
Atomic Mass22.9924.3126.9820.0930.9732.0735.4539.95

Elements in Group 1 (periodic table) have similar chemical properties and are called alkali metals . Elements in Group 2 have similar chemical properties, they are called the alkaline earth metals .

##### Short form periodic table

The short form periodic table is a table where elements are arranged in 7 rows, periods, with increasing atomic numbers from left to right. There are 18 vertical columns known as groups. This table is based on Mendeleev’s periodic table and the periodic law.

### Long form Periodic Table

In the long form, each period correlates to the building up of electronic shell; the first two groups (1-2) (s-block) and the last 6 groups (13-18) (p-block) make up the main-group elements and the groups (3-12) in between the s and p blocks are called the transition metals. Group 18 elements are called noble gases, and group 17 are called halogens. The f-block elements, called inner transition metals, which are at the bottom of the periodic table (periods 8 and 9); the 15 elements after barium (atomic number 56) are called lanthanides and the 14 elements after radium (atomic number 88) are called actinides .

### References

1. Petrucci, Ralph H., William S. Harwood, F. G. Herring, and Jeffrey D. Madura. General Chemistry: Principles and Modern Applications. 9th ed. Upper Saddle River: Pearson Education, Inc., 2007.
2. Sisler, Harry H. Electronic structure, properties, and the periodic law. New york; Reinhold publishing corporation, 1963.
3. Petrucci, Ralph H., Carey Bissonnette, F. G. Herring, and Jeffrey D. Madura. General Chemistry: Principles and Modern Applications. Custom Edition for CHEM 2. Pearson Learning Solutions, 2010.
4. Mendeleev’s 1869 Periodic Table. In Wikimedia Commons. Retrieved 4 December 2010, from  http://commons.wikimedia.org/wiki/Fi…odic_table.png .
5. Periodic Table of Elements. In Wikimedia Commons. Retrieved 4 December 2010, from  http://commons.wikimedia.org/wiki/Pe…le_of_Elements .

### Problems

1) The periodic law states that

1. similar properties recur periodically when elements are arranged according to increasing atomic number
2. similar properties recur periodically when elements are arranged according to increasing atomic weight
3. similar properties are everywhere on the periodic table
4. elements in the same period have same characteristics

2) Which element is most similar to Sodium

1. Potassium
2. Aluminum
3. Oxygen
4. Calcium

3) According to the periodic law, would argon be in front of potassium or after? Explain why.

4) Which element is most similar to Calcium?

1. Carbon
2. Oxygen
3. Strontium
4. Iodine

5) Who were the two chemists that came up with the periodic law?

1. John Dalton and Michael Faraday
2. Dmitri Mendeleev and Lothar Meyer
3. Michael Faraday and Lothar Meyer
4. John Dalton and Dmitri Mendeleev