As we look at our periodic table all the time, it's time to learn about its Trend..... yea... I know... let's do it!
Metallic:
From left to right across the table are metallic to non-metallic, which are metal to non-metal -As they going down, they will be more likely metal.
Atomic Radius:
The Atomic radius will decrease from the left to right,
and increase from the top to bottom.
Reactivity:
The reactivity is increasing from the middle to left and right,
- from the top to the bottom in metallic group
- from the bottom to the top in non-metallic group
Melting and Boiling Point:
The middle of the periodic table has the highest melting point, and it'll gradually decrease from the middle to the right and left side of the periodic table.
Ionization energy: (energy needed to be removed)
Ionization energy increases from the left bottom to the top, and from the left to the right.
Basically, Fr has the lowest ionization energy and He has the highest.
Electronegativity:
The Electronegativity increases from the left bottom to the top, and from the left to the right.
- its trend are same as ionization energy !
Core Notation:
As we know that, writing a complete electron configuration takes a bit time and it's easy to make mistakes even we memorize it. So Core Notation can save us sometimes.
Basically it uses another element from the group "Nobel gas" before itself to replace the first part of electron configuration, and doesn't affect the electrons number of the original atom.
For example:
Electron Configuration : Al = 1s2 2s2 2p6 3s2 3p1
Core Notation: Al = [Ne] 3s2 3p1
Electron Configuration: O = 1s2 2s2 2p4
Core Notation: O = [He] 2s2 2p4
Electron Configuration : K = 1s2 2s2 2p6 3s2 3p6 4s1
Core Notation : K = [Ar] 4s1
little notes: the number of the noble gas is actually repersenting the first part of the electron configuration, so once they add up, the electrons number won't be affected as a result.
In chemistry, valence electrons are the electrons of an atom that can participate in the formation of chemical bonds with other atoms. Basically, as we know from the Bohr diagram, to be able to achieve a reaction, both reactant needed to have either Open shell or Closed shell to allow or provide electrons. And to predict the valence electrons, we used to draw a diagram, but now we have one more method from electron configuration.
Frist we have to know the role, valence electrons are not counted in the d- and f- subshells. which only refer to s- and p-.
For example:
Electron Configuration : Al = 1s2 2s2 2p6 3s2 3p1
Core Notation: Al = [Ne] 3s2 3p1
From here [Ne] 3s2 3p1, 2 + 1 = 3
so the valence electrons are 3 from Al
Electron Configuration: O = 1s2 2s2 2p4
Core Notation: O = [He] 2s2 2p4
Valence electrons = 2 + 4 = 6
Electron Configuration : K = 1s2 2s2 2p6 3s2 3p6 4s1
Core Notation : K = [Ar] 4s1
Valence electrons = 1
As we used to draw Bohr diagram to predict the way of electrons display, it somehow takes me a bit of time to figure out the answer. But now, we're going to learn about a new method, Electron Configuration.electron configuration is the arrangement of elecrons of an atom, a molecule, or other physical structure. It concerns the way electrons can be distributed in the orbitals of the given system.
First of all, we have to know what is "Shell",
it is a value of N and Subshell is a set of orbitals of the same type, which are "s, p, d, f" that we are going to use it to show how it works.
Basically, we use these terms "s, p, d, f" to show electrons in the atom.
Let see what's the difference between them!
n=1 s-type > can fill 2 electrons
n=2 s, p type > can fill 6 electrons
n=3 s, p, d type > can fill 10 electrons
n=4 s, p, d, f type > can fill 14 electron
And now lets take a look the order of their pattern
So, the pattern is 1s2 > 2s2 > 2p6 > 3s2 > 3p6 > 4s2 > 3d10........................
And now we can do some excerises!
Oxygen, with 8 electrons. > 1s2 2s2 2p4 : 2+2+4 = 8 (little notes, s,p,d,f doesn't have to fully fill)
ž1 Aristotle believed an ancient Greek theory that atom
being different sizes, regular geometric shapes
and being in constant motion.
ž
believed that matter was made of different
combo of earth, air, fire and water. They represent four
qualities: dryness, hotness,coldness, and wetness. He didn’t really contribute much to the atoms
Democritus Contribution
He suggested that matters are made up of atoms, which we are still using this concept today. However, he never made any attempt to determine whether his theory was correct.
Antoine Lavoisier 1763
žproposed the Combustion Theory which was based on sound mass measurements
žHe named oxygen.
žalso proposed the Law of Conversation of Mass
which represents the beginning of modern chemistry
John Dalton 1766 - 1844
žJohn Dalton is considered the Father of Modern Atomic theory.
ždiscover the partial pressures of gases. This major advance in stoichiometry, the ratio of elements, lead to his formulation of a working theory of the atom.
J.J. Thomson 1897
žhe showed that cathode rays are rapidly moving particles, and, by measuring their displacement by electric and magnetic fields,
he determined that these particles were nearly 2,000 times less massive than the lightest known atomic particle,
which now what we call, electrons.
Ernest Rutherford 1909
ždiscovered that there were different types of rays; Alpha, Beta, and Gamma
ždiscovered that radioactive elements have half-life which can be used to find the age of an element and this method still be using widely today.
Niels Bohr 1885 - 1962
žBohr’s atomic theory can be described as one of the most important theories all over the world.
žThe Bohr Model is an approximation to quantum mechanics that has the virtue of being much simpler. He postulated based on quantum theory that electrons travel around an atomic nucleus in a stationary orbit. His work also led to the theory of different energy levels in atoms that is if an electron drops from a higher to a lower orbit, it must release energy.
