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How many elements are in the periodic table?

There are 103 elements in the periodic table

Dstar4u:

There are 103 elements in the periodic table

Since June 2011,the periodic table has 118 elements.Some of these elements occur naturally;while others are synthesized by human technology.

pls wat paul'n principle talking abt?

SLEEMYDRIZ:

pls wat paul'n principle talking abt?

There are 4 quantum numbers that characterize the energy of an electron.They are
1.principal quantum number(n) that determines the energy levels or shell.So,if two electrons are in the same shell,they're said to have the same value for the principal quantum number.The value may be 1,2,3,4 and so on.
2.The Subsidiary quantum number(L).It shows the number of energy sublevels in a shell.So,if two electrons are in the same sublevel,they're said to have the same value for the subsidiary quantum number.
3.The magnetic quantum number(m) shows d number of orbitals in a subshell.
4.The spin quantum number(s) has only two values.It determines the direction of spin of electrons in an orbital.An orbital can hold only two electrons.These two electrons spin in opposite directions;so they CAN'T HAVE THE SAME VALUE for the spin quantum number.

Continuation:
Pauli Exclusion Principle state that two electrons in the same orbital cannot have the same values for the 4 quantum numbers.
This means that even if they have the same values for n,L & m;their values for S must be different-because the electrons spin in opposite directions & can't have the same spin quantum number.

what of aufbau principles.

@richy:

what of aufbau principles.

In atoms,there are energy levels(also called shells) like K,L,M,N & so on.They are divided into subshells e.g s,p,d & f;which in turn are divided into orbitals.For example,the p-sublevel is divided into 3 orbitals Px,Py & Pz.
Energy level K has lower energy than L;L in turn has lower energy than M and so on.
There is also energy differences between the sublevels in an energy level & btw the orbitals in a sublevel.

Simply stated,Aufbau Principle says that in the building up of atom,electrons enter orbitals of low energy b4 entering orbitals of higher energy.That is,electrons are fed into orbitals starting at the lowest energy levels b4 filling higher energy levels.So,electrons would enter 1S orbital b4 entering 2S,2P,3S and so on.

It seems there are chemist on dis thread & i wud lik 2 be here alwayz. Tel me abt quantum chemistry

MyFidelis:

Simply stated,Aufbau Principle says that in the building up of atom,electrons enter orbitals of low energy b4 entering orbitals of higher energy.That is,electrons are fed into orbitals starting at the lowest energy levels b4 filling higher energy levels.So,electrons would enter 1S orbital b4 entering 2S,2P,3S and so on.

I have a query regarding dis particular principle.
Well, In atoms of some elements e.g transition metals, the 4s orbital is filled wit electrons before the 3d orbital despite the fact that the 3d orbital is at a lower energy level (i.e n=3) than the 4s orbital (n=4).
Can anyone explain why or is Aufbau's principle inconclusive?

4ortyse7en:

I have a query regarding dis particular principle.
Well, In atoms of some elements e.g transition metals, the 4s orbital is filled wit electrons before the 3d orbital despite the fact that the 3d orbital is at a lower energy level (i.e n=3) than the 4s orbital (n=4).
Can anyone explain why or is Aufbau's principle inconclusive?

U're right 2 have mentioned that electron enter the 4s orbitals before entering the 3d orbital(in transition elements).The reason is,the 4s orbital has lower energy than the 3d orbital.

Dstar4u:

It seems there are chemist on dis thread & i wud lik 2 be here alwayz. Tel me abt quantum chemistry

Energy (for example,energy of radiation from an atom) exists in packs or units called quantua(singular:quantum).

MyFidelis:

U're right 2 have mentioned that electron enter the 4s orbitals before entering the 3d orbital(in transition elements).The reason is,the 4s orbital has lower energy than the 3d orbital.

Alrite, u are explaining based on Aufbau's principle, I mean according to Aufbau's principle 4s is at a lower energy level than 3d but in reality when comparing the principal quantum number values i.e n=4 & n=3 respectively and considering d fact dat the principal quantum number(n) defines the energy level of an electron.
Thus since 4s has a higher value of n than 3d, it can therefore b concluded that 4s is at a higher energy level than 3d.

Explain how to generate electricity from nuclear fusion

4ortyse7en:

Alrite, u are explaining based on Aufbau's principle, I mean according to Aufbau's principle 4s is at a lower energy level than 3d but in reality when comparing the principal quantum number values i.e n=4 & n=3 respectively and considering d fact dat the principal quantum number(n) defines the energy level of an electron.
Thus since 4s has a higher value of n than 3d, it can therefore b concluded that 4s is at a higher energy level than 3d.

Aufbau principle is correct. 4s orbital is at a lower energy that 3d (don't mind the principal quantum number;every law has an exception).

Whats d difference between 'dimerize' and 'polymerize'?

1. how can one modify the acetamido group of chitin to make it suitable as a degradable bio-polymeric materials when cross linked with alginate?

2. what are the advantages of using viscose process to produce rayon from cellulose?

3. How to preserve fresh tomatoes from loosing taste, color and firmness for atleast 36 weeks, explain the mechanism and kinetic involves?

4. what are the structural similarities and differences btwn chitosan and chitin and what makes them bio-compatible?

5. why is the atomic number of hydrogen 1?

Good morning in the house! Please I will like if anyone can post the 2021 WAEC GCE NOV/DEC Second series chemistry past question or the marking scheme. Please sir/ma it can be sent here or to WhatsApp 08067968113. Thank you in anticipation