How to Draw Oxygen Atom
Carl Wilhelm Scheele and Priestley Joseph both independently discovered oxygen in 1771 and 1774 respectively, although Priestly's discovery received more widespread recognition. By heating mercuric oxide (HgO), they were both able to synthesize oxygen gas.
The gas was given different names by both scientists. Priestley referred to the gas as 'dephlogisticated air,' whereas Scheele referred to it as 'fire air.' Later, Antoine Lavoisier coined the term oxygen in 1774. To produce oxygen on a commercial scale, fractional distillation of liquid air and electrolysis of water, or heating potassium chlorate (KClO3) have recently been utilized.
At standard temperature and pressure, oxygen occurs in a gaseous state consistin0g of two oxygen atoms (O2). In nature, oxygen exists as a mixture of isotopes 16O, 17O, and 18O with atomic masses of 15.995, 16.999, and 17.999 amu, respectively, and relative abundance of 99:763 percent, 0.037 percent, and 0.200 percent. It comprises about 46.7% of the earth's crust which makes it the third most plentiful element.
About 87 % of the oceans (as H2O, water) and 20 % of the Earth's atmosphere are made up of oxygen (as O2, molecular oxygen O2, or ozone O3). Metal oxides, silicates (SiO4 —-), and carbonates (CO3 —) are common oxygen compounds found in rocks and soil. Frozen water is a prevalent solid on the outer planets and comets. In addition, the oxygen spectrum can often be detected in stars.
Oxygen is a highly reactive element that is essential for combustion, respiration, and the formation of oxides. During the steelmaking process, streams of high-pressure oxygen are used to remove impurities from molten pig iron. An extremely hot flame is required during welding, which can be obtained through the reaction of oxygen and acetylene (C2H2). Similarly, combining liquid oxygen and liquid hydrogen yields excellent rocket fuel.
Aside from these one of the oxygen allotrope, Ozone (O3) forms a thin, protective layer surrounding the earth that protects the surface from UV radiation.
In this article, we are going to draw and interpret the oxygen Bohr model that helps us to understand what happens in an atom.
Bohr atomic model of oxygen atom
Bohr atomic model is the revised version of the Rutherford model that includes a visual representation of its subatomic particles. A single atom is composed of a positively charged proton, negatively charged electron, and neutron with no charge.
The inner part of an atom is called a nucleus which is a positively charged sphere inside which proton and neutron are packed, while electrons revolve around the nucleus in a fixed shell with a fixed size and energy. The names assigned to the shell are K, L, M, N, etc., or 1, 2, 3, 4, 5, etc. The energy of the shell depends on its size of the shell.
The first shell which is closer to the nucleus is smaller in size so it has the lowest energy and is also called the ground state. As the distance increases from the nucleus, the size of the shell also increases, hence energy also increases. Each shell can hold a maximum number of electrons and is governed by formula 2n2 where n is the number of shells.
Proton and neutron can't move from one place to another, which means they are localized, while electrons can jump from lower energy level to higher energy level or vice versa, only when they absorbed or release photons. The energy is calculated using Plank's equation
ΔE = E2 – E1 = h ν
Where ΔE = gains or loss of energy
E1 = Energy of lower shell
E2 = Energy of higher shell
h = Plank's constant
ν = Frequency of electromagnetic radiation gain or loss
Now, let's look up to the oxygen Bohr model. Actually, Bohr has proposed his model only for the hydrogen atom. So, there is no Bohr atom of oxygen. However, we try to draw and interpret Bohr's model of oxygen atom by following his assumptions.
Steps to draw oxygen Bohr model
- Determine the number of protons, electrons, and neutrons of an atom
- Protons: The number of protons is determined by the following relation.
That means the number of protons is equal to the atomic number.
For the oxygen atom, the periodic table assigns the atomic number 8. Hence, the nucleus of the Oxygen atom possesses 8 protons.
For a fixed atom, the proton number is fixed. A new element will be produced if a proton is gained or lost. For example, adding one proton to an Oxygen atom results in the formation of a Fluorine(F) atom, whereas removing one proton results in the formation of a new Nitrogen (N) atom.
- Neutron: the number of neutrons is determined by the following relation;
Subtraction of the number of protons from the atomic mass yields the number of neutrons. This is due to the fact that protons and neutrons both weigh 1amu (atomic mass unit), whereas electrons weigh almost nothing.
For 16O (most abundant), atomic number = 8, atomic mass=15.994 (rounded to 16) and protons = 8
Number of neutrons = (16-8) =8
If there is a gain or loss of neutrons in an atom, it will change to isotopes rather than forming a new atom. In the case of the oxygen atom, a gain of one neutron gives 17O isotope, and a gain of two neutrons leads to isotope 18O.
- Electron: For a neutral atom, the number of electrons can be determined by the following relation.
The proton number of the Oxygen atom is 8, hence 8 electrons are moving around the nucleus.
If the number of neutrons in an atom changes, the atom ceases to be neutral and transforms into an electrically charged entity known as ions. Positively charged ions (cations) and negatively charged ions (anion) are the two types of ions. The number of electrons in cations equals the number of protons minus the charge, whereas the number of electrons in anions equals the number of protons plus the charge's absolute value.
- Draw a nucleus
In this step, draw a circle to represent an atom's nucleus. Add the proton and neutron numbers in the center of the circle to complete the nucleus structure. Figure 2 depicts the nucleus of 16O.
- Draw the first shell with an electron
The second circle is drawn outside the nucleus and is known as the first shell or K-shell. This shell is the closest to the nucleus and has the least energy of the others. Determine the maximum number of electrons that it can hold:
K-shell, n=1, 2n2 = 2 X (1)2 = 2
That means k-shell can hold up only two electrons.
In the case of the oxygen atom, it has a total of eight electrons. So, two electrons from it fit in the first shell in paired form.
As a result, we are left with six electrons because two of the eight electrons are used up in the first shell. Let's put the remaining six electrons in the subsequent shell of the oxygen atom.
- Draw the second shell with an electron
The third circle is drawn after the first shell which represents the second shell or L-shell. It has high energy as compared to the first shell. Now, determine the maximum number of electrons that it can hold:
L-shell, n=2, 2n2 = 2 X (2)2 = 8
That means L-shell can hold up to eight electrons.
A pattern of the fitting electron after the first shell is clockwise. We should fit the electrons one by one on each of the four sides (top-right-bottom-left) at a 90°, then start pairing them.
In the case of the oxygen atom, L-shell is fitted with six electrons in a clockwise pattern.
The final Bohr model for the oxygen atom is shown in the diagram below:
That's all, this is ourBohr model of the Oxygen atom that contains 8 protons and 8 neutrons at its core nucleus, and is surrounded by the K-shell with one paired electron and the L-shell with two pairs of an electron and two unpaired electrons.
Oxygen Bohr Model useful for
- Calculate the number of valence electrons in the oxygen atom
A valance electron is present on the last shell of an atom. These electrons participate in any chemical reaction because they have more energy than electrons in other orbits. According to the Octet rule, an atom's outermost orbit should have a maximum of 8 electrons in order to be stable. When the outermost orbit is filled, however, chemical participation in that element is often very low or non-existent.
From the Bohr model of the oxygen atom, we can easily find out the valence electrons by looking at its outermost shell. The outermost shell of the Oxygen atom is the L shell that contains 6 electrons. Therefore, the Oxygen atom has six valence electrons.
- Calculate valency of the Oxygen atom
The number of electrons an element can lose or gain to achieve stability is referred to as valency. It is always a whole number with no positive or negative sign. By valency, we can determine how an element's atoms will react with those of another element.
Bohr's model of the Oxygen atom shows that it has 6 electrons in its outermost shell. To complete its octet oxygen needs 2 more electrons. By completing its octet, it will attain stability. Thus, the valency of oxygen is 2.
- Drawing Lewis Structure of Oxygen atom
A Lewis structure is a diagram that illustrates key concepts in understanding how atoms form bonds and lone electron pairs in a molecule.
The oxygen atom has six electrons in its valence shell, or L-shell, according to the above-drawn Bohr model. This makes it simple to draw the Lewis structure of oxygen, in which the nucleus is represented by the element's atomic symbol, and the valence shell electrons are represented by dots surrounding the nucleus. Therefore, the Lewis structure of Oxygen can be drawn as
Limitations of Oxygen Bohr Model
- No explanation of the electronic configuration
The electronic configuration is a common method of representing all of the electrons in an atom in terms of subshells. It can be used to assess an element's valency, identify the properties of a group of elements, and generate atomic spectra. In Bohr's paradigm, the electron might behave classically (orbiting the nucleus at discrete distances from the nucleus). Subshells (s, p, d, and f), orbitals, and electron spin aren't considered. This is one of the model's flaws.
Summary
- According to the Bohr Model of atoms, oxygen has a nucleus with six neutral neutrons and five positively charged protons. In addition, five negatively charged electrons orbit the nucleus in precise orbits called energy levels or shells.
- The number of protons is equal to the atomic number which is also equal to the number of electrons in an atom.
- Rounding up the atomic mass to the nearest whole number and subtracting the number of protons yields the number of neutrons.
- The formula 2n2, where n is the number of shells, can be used to compute the number of electrons that can be accommodated in any shell of an atom.
- The oxygen atom is made up of two shells, the K and L shells, which contain two and six electrons, respectively.
- The oxygen atom has six valence electrons.
- The valency of oxygen is 2.
- Lewis structure of oxygen atom can be also drawn with the help of Bohr model.
- One limitation of the Bohr model is that it does not explain the distribution of electrons in their subshells.
Source: https://tuktukstudy.com/oxygen-bohr-model/
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