1864- John Newlands put the known elements in order based on their atomic weights and other similarites.
1864- Dmitri Mendeleev made a periodic table based on element's atomic weights but he put elements with like properties under one another. His table included 66 known elements.
1894- Noble Gases were discovered by William Ramsay.
1913- Henry Moseley placed each element with their atomic number.
Beginning-1940s - New elements have been found and placed on the periodic table according to their atomic weights and properties.
Wednesday, May 23, 2012
Why are metal oxides called basic oxides, and nonmetal oxides called acidic oxides?
When metal oxides dissolve in water, they form alkaline solutions which are known as basic.
When nonmetal oxides dissolve in water, they form acidic solutions.
What is ionization energy? Which family has the greatest and which family has the lowest? Why is the second ionization of Na so much higher than the first? Why is it so difficult to take away electrons from nonmetals as compared to metals?
Ionization Energy is the energy needed to take away an electron from a molecule or ion.
Family 7A has the greatest ionization energy, and the second group of earth elements has the lowest.
The second ionization of Na is higher than the first because it is much harder to get rid of the second electron because by that time the element only wants to become neutral, which is more easily obtained by gaining an electron as opposed to losing one.
It is more difficult to take away electrons from nonmetals as compared to metals because to follow the octet rule, nonmetals must gain an electron to fill their outer shells, where metals need to lose an electron to fufill the octet rule.
Family 7A has the greatest ionization energy, and the second group of earth elements has the lowest.
The second ionization of Na is higher than the first because it is much harder to get rid of the second electron because by that time the element only wants to become neutral, which is more easily obtained by gaining an electron as opposed to losing one.
It is more difficult to take away electrons from nonmetals as compared to metals because to follow the octet rule, nonmetals must gain an electron to fill their outer shells, where metals need to lose an electron to fufill the octet rule.
What happens to the atomic radius as you move right, as you move up? What affects the size of the atoms when you move up and down a family? What affects the size as you move left and right in a period? What has a greater effect, moving up and down, or moving left and right? Why?
As you move right on the periodic table, the atomic radius decreases. Also, as you move from bottom to top of the groups on the periodic table the size of the radius becomes smaller.
When you move up and down a family on the periodic table, there are more layers of electrons being added to the outer shell of an element as you go from top to bottom.
Going from left to right on the periodic table, elements gain protons in the nucleus. This increasing positive charge pulls the shell of the atom in toward the nucleus, thus making the atomic radius slightly smaller.
Moving left to right on the periodic table has more of an effect on elements than moving up and down. It produces more drastic changes because the number of protons in the elements are changing and affecting their charges.
http://www.chem1.com/acad/webtext/atoms/atpt6.html
When you move up and down a family on the periodic table, there are more layers of electrons being added to the outer shell of an element as you go from top to bottom.
Going from left to right on the periodic table, elements gain protons in the nucleus. This increasing positive charge pulls the shell of the atom in toward the nucleus, thus making the atomic radius slightly smaller.
Moving left to right on the periodic table has more of an effect on elements than moving up and down. It produces more drastic changes because the number of protons in the elements are changing and affecting their charges.
http://www.chem1.com/acad/webtext/atoms/atpt6.html
What is Electron Affinity? What is the trend on the periodic table?
Electron Affinity is the ability of a molecule or atom to gain an electron and become a negative ion.
On the periodic table, Electron Affinity decreases from top to bottom and increases from left to right.
What is electronegativity? What is the trend on the periodic table?
Electronegativity is the ability of an atom to attract electrons and bind to them.With the exception of noble gases, electronegativity increases as you move from left to right across the periodic table and as you move from top to bottom electronegativity decreases.
http://edtech2.boisestate.edu/kilnerr/502/jigsaw.html
What happens to the radius of atoms as they become cations? anions? What are isoelectronic ions, and how can you tell which ones are largest and smallest?
When an atom becomes a cation, the radius becomes smaller, and when it becomes an anion the radius becomes larger.
Isoelectronic ions are elements that have the same electronic configurations as a different element or ion on the periodic table.
As the nuclear charge in the atoms increases, their radius decreases (as shown above), so to be able to determine which isoeletronic atom's radius is either smallest or largest, one must look at the nuclear charge of the specific atom.
Isoelectronic ions are elements that have the same electronic configurations as a different element or ion on the periodic table.
As the nuclear charge in the atoms increases, their radius decreases (as shown above), so to be able to determine which isoeletronic atom's radius is either smallest or largest, one must look at the nuclear charge of the specific atom.
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