Embedded Files
Important content:
Important content:
Periodic Table
Bohr's atomic model
Orbital model
Electron configuration of atoms
Valence electrons
Ground state and excited state
Electronegativity trend
Oxidation state
Atoms exist!
Atoms exist!
During the Lighting fields project we learned how white light separates into a continuous spectrum of colors when passing through a prism.
However, when the light passes through a substance made up of certain atoms it breaks into a discontinous spectrum creating an Emission or Absorption Spectra, which are related, as shows the image on right side. The importance here is that the patterns of lines can be related to a specific atom.
The physicist Niels Bohr proposed an atomic model that correctly explained the mentioned spectra of elements, summarized as follows:
Electrons travel around the nucleus in specific orbits, as we can see here.
Each orbit has a particular energy level or state. Higher orbits has more energy.
An electron can move towards a higher orbit if it absorbs a wave whose energy corresponds to the energy difference between the two orbits.
On the contrary, an electron can move towards a lower orbit if it emits a wave whose energy corresponds to the energy difference between the two orbits.
According to that model the absorption and emission of the EM waves by electrons produce the lines of colors.
The light can be absorbed and spontaneusly emitted repeatedly by different atoms. However, the emission can also be stimulated by a similar wave of light.
Can you find atoms in the scale of the Univers?
Can you find atoms in the scale of the Univers?
But... what is an atom?
But... what is an atom?
An atom is the smallest constituent unit of ordinary matter. Every atom is composed of:
A nucleus: made of one or more protons and typically a similar number of neutrons. Protons and neutrons are called nucleons. More than 99.94% of an atom's mass is in the nucleus.
And one or more electrons bound to the nucleus.
If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion.
The number of protons in the nucleus defines to what chemical element the atom belongs: for example, all copper atoms contain 29 protons.
More information
Make your own research!
Make your own research!
Build an atom
Build an atom
Let's try this simulator to build atoms and answer these questions:
How many electrons can you place in each orbit?
Which are the differences or similarites between periods? And groups?
What is the mass number?
What is the atomic number? Does it have a relation with electrons?
How can you change the net charge of an atom?
Are all the atoms neutral?
Write down all your learning process in your portfolio. Try all the options: atom, symbol and game!
Orbitals to improve the model
Orbitals to improve the model
Remember that Bohr's orbits were the line or path where electrons move considering they energy. Are those lines real? Can we see them?
Nowadays, research and new tecnologies help replace the concept of orbits with orbitals. it is currently accepted that an energy level does not actually correspond to a circular orbit rather than various regions of the electron cloud, with different shapes. Those electron clouds are called atomic orbitals.
But... what is an orbital? In short:
But... what is an orbital? In short:
An orbital is a 3D region around the nucleus where there is a high probability of finding an electron.
An orbital can be occupied by two electrons, that must spin in opposite.
There are four types of orbitals with different shapes: s Orbitals (spherical shape); p Orbitals (two-lobed shape); d Orbitals (different shapes) and f Orbitals (different shapes).
Each type of orbital has a specific amount of energy. The s sublevel has the lowest energy and f the maximum.
The electron configuration is the way electrons are placed in the orbitals of a certain atom.
More information
Electron configuration
Electron configuration
How should we place the electrons on the orbitals?
How should we place the electrons on the orbitals?
The maxim number of electrons for each sub shell is: s=2; p=6; d=10; f=14
An electron tends to always occupy the lowest energy orbital available.
If a sublevel has more than one orbital available, electrons tend to occupy an empty orbital rather than sharing an orbital with others.
It does not seem so complicated with an example!
It does not seem so complicated with an example!
Example: Bromine 35
1s22s22p63s23p64s23d104p5
Where:
1, 2, 3, 4.... is the principal quantum number or energy level (shell)
s, p, d... is the sublevel or subshell
2, 6, 10... shows the number of electrons in the s, p, d subshell
Valence electrons
Valence electrons
The valence electrons are those filling the atom's highest energy level. These are crucial to understand chemical bonds and chemical reactions.
Noble gas configuration is when the electron configuration ends with p6. In this case, atoms are stable and will not react or bond.
Atoms can be in:
Ground State:
Ground State:
if the electrons occupy the lowest energy orbital.
Atoms are typically in this state.
It can be related with stability.
Excited State:
Excited State:
If an electron occupies an outer sublevel, leaving the lower sublevels not fully complete.
It happens when an atom is transferred energy, the atom's electrons can absorb the energy and jump to higher energy orbitals.
It can be related with unstability. So it tends to go to its ground state.
Electronegativity
Electronegativity
Electronegativity can be defined as the power of an atom in a molecule to attract electrons itself
Linus Pauling, the Nature of the Chemical Bond
An atom's electronic configuration is related to its electronegativity.
The greater the electronegativity of an element, the less electrons it needs to achive a noble gas configuration.
Noble gases do not have an electronegativity value because of their naturally stable electron configuration.
Review the Periodic Table. In which group can we find the most electronegative elements?
Exactly! That is, the group 17 as they only have to gain one electron to achieve a noble gas configuration.
Oxidation state trends in the Periodic Table
Oxidation state trends in the Periodic Table
To understand the meaning of oxidation let's have a look at Wikipedia description:
The oxidation state, sometimes referred to as oxidation number, describes the degree of oxidation (loss of electrons) of an atom in a chemical compound.
Conceptually, the oxidation state, which may be positive, negative or zero, is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. This is never exactly true for real bonds.
Assess your learning proCESS
Assess your learning proCESS
Building Chemistry
Building Chemistry
PART 1: The main protagonists
PART 1: The main protagonists
Each student would have to explain an atom according to the conceptual framework of this part. It is important to highlight that you will have to apply the contents of this part. As always: be visual and creative!
And... go further asking more questions on this topic and finding the answers!!!
And... go further asking more questions on this topic and finding the answers!!!
Report abuse