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Periodic Table - Mendeleev's Predictions

atomic elements mass based

Mendeleev came to believe in his periodic table to such a degree that he changed the atomic mass of known elements so that they fit where they "belonged" in his table. He did this with no experimental evidence, only his belief in his table. In one such case he changed the atomic mass of beryllium (Be) from 14, which placed it in Group 15 above nitrogen (N), to 9. This placed it in Group 2 above magnesium (Mg) with which it was more closely related chemically. Even more daring was the fact that Mendeleev predicted the properties of undiscovered elements. Based on gaps in the periodic table Mendeleev deduced that in these gaps belonged elements yet to be discovered. Based on other elements in the same group he predicted the existence of eka-aluminum, eka-boron, and eka-silicon, later to be named gallium (Ga), scandium (Sc), and germanium (Ge). Mendeleev predicted the atomic mass of each element along with compounds they each should form. Within 15 years of Mendeleev's predictions, these elements were discovered, and their properties were found to closely match his predictions. These fulfilled predictions went a long way toward convincing any remaining doubters of the infallibility of the periodic table.

Another change Mendeleev made based on chemical analogy and intuition was placing iodine (I) after tellurium (Te), even though the atomic mass of iodine was less than tellurium. This anomaly, along with the difficulty of where to place the inner transition metals, were problems that would soon be definitively solved. At the time of the periodic table's construction, little was known of atomic structure. With further scientific discoveries such as the existence of protons and the existence of electronic shells, these mysteries were explained and placed into their current places in the periodic table.

Refinement in the measurements of atomic mass, the ordering of the elements based on atomic number rather than atomic mass by Henry G. Moseley (1887-1915) in 1913, and the discovery of new elements have led to the continuing evolution of the periodic table. But since Mendeleev's time the periodic table has remained basically unchanged, providing testament to the power of his original insight.

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over 1 year ago

I am the mother of boo boo and choo choo and I thank my children for the genius idea of the periodic table wallpaper. The whole extended family follows the trend.

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over 1 year ago

i am choo choo's twin sister and i copied her idea to make it a wallpaper and now our whole house is a periodic table #goals

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over 1 year ago

i am boo boo and choo choos pet cow and i love our new house so much i painted my meadow and now i can eat the periodic table

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over 1 year ago

I LOVE THIS IT IS MY LIFE i printed it out and made wallpaper of it for my bedroom #goals

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about 9 years ago

no offence but i do understand the periodic table but im stuck on this piece of science homework to have 2 try and find missing elemants and i thought that this website might have helped me but it hasnt ! :( and if i dont get the piece of homework done by 2morrow i will get a detention :( and im not keen on detentions !

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over 5 years ago

this sucks

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over 5 years ago

this sucks

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about 5 years ago



Dimitri Mendeleev created the he created the periodic table, and organized some of it.

There are 7 rows in the periodic chart. These rows are called Table are called periods
The first element in the period is always a very active .

The more you go to the right the elements get active until you end up with a non-reactive ____________.

The Alkali Metal Family is in column number _______.

Lithium is used in the _ion batteries_ of cell phones.

The atomic # identifies the # of is the number of protons found in the nucleus of an the atom of an element.

Protons are the from what I see from the question my answer is. Protons are positively charged, electrons are negatively charged and neutrons are nuetral. charges particle found in the ________ of an atom.

Electrons are the _____ charged particle found in ________ outside the nucleus.

No 2 elements can have the same ________________.

Atomic mass is the ____________ mass of all the isotopes of an element.

Isotopes are atoms of the same element that have the same # of ________ but different # of _____________.

The alkali metals are the most ________ metals in the table and they have ____ valence electron.

Alkali metals can be very ____________ with oxygen or water.

Elements in the same family share the same # of __________ electrons.

The Transition ________ are in the middle of the table.

Metals can have 1, 2,3 or 4 ____________________.

Transition metals usually give away _____________.

Of the 109* known elements ______ are metals. (* actually 118 as of 4/01)

The 1st physical property of all metals is ______________.

Ductile means that metal can be drawn into thin __________.

Malleable means that metals can be hammered into _________________.

Most metals allow heat and _____________ to flow through them.

Valence electrons are electrons on the __________ energy level.

Valence electrons can be gained or lost when elements _______ with each other.

Non-metals are dull and they don’t conduct ________ or electricity.

Nitrogen makes up ______ of the earth’s atmosphere.

Non-metals have __,__,__ or ___ valence electrons. They tend to _____ electrons.

Elements with 8 electrons tend to be non-____________.

_____________ is the only element in family 18 that does not have 8 valence electrons.

Metalloids can be found on either side of the __________ line.

Metalloids share properties of both metals and ___________. They conduct heat and electricity better than _____________.

Halogens are in family 17. They have ______ valence electrons.

Halogens react easily with elements in family 1 like ____________.

Whenever halogens bound with the elements in family 1 they form a _____.

Family 18 are non-metals and have ____ valence electrons, except helium.

__________________ are also called “inert gases.”

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almost 2 years ago

this sucks

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about 1 year ago

same as carrie i need 2 predict the missing elements and this didn't help. HOW did he do it?

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about 1 year ago

same as carrie i need 2 predict the missing elements and this didn't help. HOW did he do it?