1. Dimitri Mendeleev was the first to publish an organized periodic table and predicted the properties of undiscovered elements.
2. Henry Moseley later arranged the periodic table by atomic number, which is the modern version.
3. The periodic law states that when elements are arranged by atomic number, they display a repeating pattern of chemical and physical properties.
In this ppt my aim is to show you that about periodic trend ,periodic laws ,metal nonmetal & metalloids ,periodic table,valence electrons ,vb theory & About atomic radius,size etc and about types of bonds ,types of enthalpy ,formation of electrons,rules and many more
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Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
In this ppt my aim is to show you that about periodic trend ,periodic laws ,metal nonmetal & metalloids ,periodic table,valence electrons ,vb theory & About atomic radius,size etc and about types of bonds ,types of enthalpy ,formation of electrons,rules and many more
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
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Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
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Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
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The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
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2. The Periodic Law
• Dimitri Mendeleev was the first scientist to
publish an organized periodic table of the
known elements.
• He was perpetually in trouble with the
Russian government and the Russian
Orthodox Church, but he was brilliant
never-the-less.
3. The Periodic Law
• Mendeleev not only predicted the existence
of 2 (at the time) undiscovered elements,
but he predicted the properties too, and he
was right!
• He was very accurate in his predictions,
which led the world to accept his ideas
about periodicity and a logical periodic
table.
4. The Periodic Law
• Mendeleev
ordered a
periodic table
according to
atomic mass,
which makes
sense (look at a
few in a row)
6. • In 1913, Henry Moseley decided to arrange
the periodic table by the number of protons,
a.k.a The atomic number
• This is the version that we use today
The Periodic Law
7. The Periodic Law
• Mendeleev and Moseley understood the
‘Periodic Law’ which states:
• When arranged by increasing atomic number,
the chemical elements display a regular and
repeating pattern of chemical and physical
properties.
8. The Periodic Law
• “Which elements act alike?” Lab
• Review
• Precipitate
• Cation
• Family names
9. The Periodic Law
• “Which elements act alike?” Lab
• What’s new?
• Soluble (s) vs insoluble (i)
• Polyatomic ions
• Poly(many)atomic(atoms) ions(charged molecules)
• Phosphate, Carbonate, Nitrate
10. The Periodic Law
“Which elements act alike?” Lab
• Things to focus on
• The Cations
• Where are they on the periodic table?
– Are they reacting similarly in the same group/family or the
same period (row)?
11. The Periodic Law
• “Which elements act alike?” Lab
• Goggles on, Closed toed shoes on and…
GO FORTH AND SCIENCE!
12. The Periodic Law
• Atoms with similar properties appear in
groups or families (vertical columns) on the
periodic table.
• They are similar because they all have the
same number of valence (outer shell)
electrons, which governs their chemical
behavior.
13. Valence Electrons
• Do you remember how to tell the number of
valence electrons for elements in the s- and
p-blocks?
• How many valence electrons will the atoms
in the d-block (transition metals) and the f-
block (inner transition metals) have?
• Most have 2 valence e-, some only have 1.
14. A Different Type of Grouping
• Besides the 4 blocks (s,p,d,f) of the table,
there is another way of classifying element:
• Metals
• Nonmetals
• Metalloids or Semi-metals.
16. Metals, Nonmetals, Metalloids
• There is a zig-zag or
staircase line that
divides the table.
• Metals are on the left
of the line, in blue.
• Nonmetals are on the
right of the line, in
orange.
17. Metals, Nonmetals, Metalloids
• Elements that border
the stair case, shown
in purple are the
metalloids or semi-
metals.
• There is one important
exception.
• Aluminum is a metal
18. Metals, Nonmetals, Metalloids
• How can you identify a metal?
• What are its properties?
• What about the less common nonmetals?
• What are their properties?
• And what is a metalloid?
19. Metals
• Metals are lustrous
(shiny), malleable,
ductile, and are good
conductors of heat and
electricity.
• They are mostly solids
at room temp.
• What is one
exception?
20. Nonmetals
• Nonmetals are the
opposite.
• They are dull, brittle,
nonconductors
(insulators).
• Some are solid, but
many are gases, and
Bromine is a liquid.
21. Metalloids
• Metalloids, aka semi-metals
are just that.
• They have characteristics of
both metals and nonmetals.
• They are shiny but brittle.
• And they are
semiconductors.
• What is our most important
semiconductor?
22. Periodic Trends
• There are several important atomic
characteristics that show predictable trends
that you should know.
• The first and most important is atomic
radius.
• Radius is the distance from the center of the
nucleus to the “edge” of the electron cloud.
23. Atomic Radius
• Since a cloud’s edge is difficult to define,
scientists use define covalent radius, or half
the distance between the nuclei of 2 bonded
atoms.
• Atomic radii are usually measured in
picometers (pm) or angstroms (Å). An
angstrom is 1 x 10-10 m.
24. Covalent Radius
• Two Br atoms bonded together are 2.86
angstroms apart. So, the radius of each
atom is 1.43 Å.
2.86 Å
1.43 Å 1.43 Å
25. Atomic Radius
• The trend for atomic radius in a vertical
column is to go from smaller at the top to
larger at the bottom of the family.
• Why?
• With each step down the family, we add an
entirely new energy level to the electron
cloud, making the atoms larger with each
step.
26. Atomic Radius
• The trend across a horizontal period is less
obvious.
• What happens to atomic structure as we step
from left to right?
• Each step adds a proton and an electron
(and 1 or 2 neutrons).
• Electrons are added to existing sublevels.
(They are not getting bigger)
27. Atomic Radius
• The effect is that the more positive nucleus
has a greater pull on the electron cloud.
• The nucleus is more positive and the
electron cloud is more negative.
• The increased attraction pulls the cloud
in, making atoms smaller as we move from
left to right across a period.
28. Effective Nuclear Charge
• We call this effect…
• Effective nuclear charge is the pull that an
electron “feels” from the nucleus.
• The closer an electron is to the nucleus, the
more pull it feels.
• As effective nuclear charge increases, the
electron cloud is pulled in tighter.
29. Atomic Radius
• Here is an animation to explain the trend.
• It might help to draw arrows like this:
30. Practice…
1. Explain why a magnesium atom is smaller
than atoms of both sodium and calcium
2. Predict the size of the astatine (At) atom
compared to that of tellurium (Te). Explain your
prediction.
3. Which effect on atomic size is more
significant, an increase in nuclear charge across
a period or an increase in occupied energy levels
within a group? Explain.
31. Ionization Energy
• This is the second important periodic trend.
• If an electron is given enough energy to
overcome the effective nuclear charge
holding the electron in the cloud, it can
leave the atom completely.
• The atom has been “ionized” or charged.
• The number of protons and electrons is no
longer equal.
32. Ionization Energy
• The energy required to remove an electron
from an atom is ionization energy. (measured
in kilojoules, kJ)
• The larger the atom is, the easier its electrons
are to remove.
• Ionization energy and atomic radius are
inversely proportional.
35. Ionization Energy
• If an atom as a low ionization energy, will it
be easy or hard to remove an electron?
• Think about the energy required to remove it, is it
high or low? Do you have to put a large amount of
energy into it or a small amount?
• What if the atom has a high ionization energy?
36. Practice…
1. Compare the first ionization energy of
sodium to that of potassium.
2. Compare the first ionization energy lithium
to that of beryllium.
37. Metallic Character
• This is simple a relative measure of how
easily atoms lose or give up electrons.
• Your help sheet should look like this:
Which
element is
most
metallic?
38. Electronegativity
• Electronegativity is a measure of an atom’s
attraction for another atom’s electrons.
• It is an arbitrary scale that ranges from 0 to 4.
• Generally, metals are electron donators and
have low electronegativities.
• Nonmetals are electron takers and have high
electronegativities.
• What about the noble gases?
• Do they need any electrons?
40. Electronegativity
• What is the most electronegative atom?
• Why?
• Fluorine
• It has a small atomic radius, and a high (relative)
effective nuclear charge
41. Practice…
1. Is the electronegativity of barium larger or
smaller than that of strontium? Explain.
2. Arrange oxygen, fluorine, and sulfur in
order of increasing electronegativity.
42. Overall Reactivity
• This ties all the previous trends together
in one package.
• However, we must treat metals and
nonmetals separately, as one will gain
electrons and one will lose electrons.
• The most reactive metals are the largest
since they are the best electron givers.
• The most reactive nonmetals are the
smallest ones, the best electron takers.
44. Overall Reactivity
• Take out a piece of scrap paper or just find
a spot in your notes…
• We are going to watch a video that will
react sodium, potassium, rubidium, and
cesium with water.
• Prediction: Order the 4 elements from least
reactive to most reactive.
• Justify your reasoning!
45. Alkali metal video
• Extra link (slow motion):
http://www.youtube.com/watch?v=iP6CRZ
dDu6o
46. Ionic Radius
• Cations are always smaller than the original
atom.
• The entire outer PEL is removed during
ionization.
• Conversely, anions are always larger than
the original atom.
• Electrons are added to the outer PEL.
47. Cation Formation
11p+
Na atom
1 valence electron
Valence e-
lost in ion
formation
Effective nuclear
charge on remaining
electrons increases.
Remaining e- are
pulled in closer to
the nucleus. Ionic
size decreases.
Result: a smaller
sodium cation, Na+
48. Anion Formation
17p+
Chlorine
atom with 7
valence e-
One e- is added
to the outer
shell.
Effective nuclear charge is
reduced and the e- cloud
expands.
A chloride ion is
produced. It is
larger than the
original atom.
49. Practice…
1. Explain why the sulfide ion (S-2) is larger
than the chloride ion (Cl-).
2. Would you expect a S-2 ion to be larger or
smaller than an K+ ion? Explain.
50. Apply…
• Would you expect a Cl- ion to be larger or
smaller than an Mg+2 ion? Explain.