Predicting Valence Electrons(kevin)

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Electronic Structure of the Atom

In this Chapter, we have learned the energy level of the electrons surrounding the nucleus. Different elements have different electronic energy level. An Energy Level is the amount of energy, which an electron in an atom can possess. ("n" is the number of the energy level). The energy difference between two particular enegy level is called the quantum of energy.

                                                                What is energy level?

Quantum of energy

In atomic physics and quantum chemistry, electron configuration is the arrangement of electrons of an atom, a molecule, or other physical structure. It concerns the way electrons can be distributed in the orbitals of the given system (atomic or molecular for instance).

For example:  H hydrogen is 1s¹
                              C carbon is 1s² 2s² 2p²
                      Mg magnesium is 1s² 2s² 2p⁶ 3s²
                            

Ground State：
when all the electrons of an atom are in their lowest possible energy levels

Excited State:

when one or more of an atom's electrons are in energy levels other than the lowest available level.

Types of Orbitals:

An atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus. The term may also refer to the physical region defined by the function where the electron is likely to be.

Predicting the Number of Valence Electrons:

In chemistry, valence electrons are the electrons of an atom that can participate in the formation of chemical bonds with other atoms. Valence electrons are the "own" electrons, present in the free neutral atom, that combine with valence electrons of other atoms to form chemical bonds. In a single covalent bond both atoms contribute one valence electron to form a shared pair. For main group elements, only the outermost electrons are valence electrons. In transition metals, some inner-shell electrons are also valence electrons.

The videos below are examples of how to find valence electrons from the electron configuration:

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Atomic Structure

Today we have learn the atomic structure of an atom. There are three parts to consist an atom: Proton, Neutron and Electron.

Atomic Number: The number of protons found in the nucleus of an atom that atoms have no overall electrical charge. Atomic Number= number of protons= number of electrons

Subatomic Particles

Ions:
Most atoms are capable of either gaining or losing electrons. A few elements, like hydrogen, are able to do both. They can do this by accepting electrons from , or giving electrons to, other atoms. Atoms that have gains or lost electrons are called ions.

Mass Number:
The mass number (A), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus.

Atomic Mass:
The atomic mass (m_a) is the mass of a specific isotope, most often expressed in unified atomic mass units.The atomic mass is the total mass of protons, neutrons and electrons in a single atom (when the atom is motionless).

Isotopes:
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation of the atom as a particular element.

Atomic Theory

Greek philosophers believed that atomos that were the smallest pieces of matter.
- Aristotle who believed in four element of earth, air, fire and water
- Alchemist who desired to turn common metals into gold
Their activities marked the beginning of our understanding of matter

But it is not a scientific theory because it could be tested through  observation.

There are a Earliest theory about atomic theory who is Democritus, a 300 b.c. greek philosopher who said that atoms are invisible particles.

Later in the late 1700s came Lavoisier after Democritus, he stated the first version of the law of conservation of mass and Law of difineite proportions

After that, Proust in 1799 proved that Lavoisier's Laws by experiments.
Follow up is Dalton in early 1800s who defined atoms as solid and indestructible spheres base on the Law of Conservation of Mass

Later, J.J. Thomson (1850s)  rose the first theory that have positive and negative charges in atoms and demonstrated the existance of electrons using a cathrode ray tube.

Rutherford in 1905 shwoed atoms have a positve, dense center with electrons outside it and ecplains why electrons spin around nucleus and suggested atoms are mostly empty space.

Atomic Theory IV
Neils Bohr (1885-1962), studied gaseous smaple of atoms, which were made to glow by passin gan electronic current through them.

That's about all of the history of chemists in the earlier eras. These are the ones of the greatest chemists in human history. We learn new things from them. Even the scientists today apply these theories into their experiement and exploration of chemistry. So it is worthwhile to learn about them. I hope you have learned something from this particular blog.

Percent Yield & Percent Purity

Percent Yield is the calculation of the amount of product produced to the amount of product one expected.



FORMULA
                         grams of actual product recovered
Percent Yield= -----------------------------------------------  x 100%
                         grams of product expected from stoichiometry

On the other hand, Percent Purity is the percentage of the mass of a substance to the mass of the impure substance. This means there are usually some impure substances in a chemical reaction. But we need to calculate the amount of impure substance in an equation for example.

 FORMULA:
                 mass of Pure Substance
% purity=----------------------------- x 100%
                 mass of Impure Substance


For example,

>If a 156.0 g of Cu ore contains 60.00 g of pure Cu metal. What is the percent purity?
                 60.00g of Cu
% purity=------------------ x 100% = 38.46 %
                156.0g of Cu ore
>There are 6.5 grams of impure Zn, the percent purity is 87%, what is the mass of the pure Zn?
                       x
87%= -----------------------
              6.5 g of Impure Zn

so x= 0.87 * 6.5g Impure Zn
     x= 5.6g of pure Zn