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26th Mar 2019 @ 17 min read
Everything around us, in the earth, and beyond earth is matter. Matter consists of atoms. Every type of atom is associated with an element. There are 118 elements known to us, and they are arranged in the modern periodic table. This article mentions some of the most abundant elements in different systems.
Hydrogen is the most abundant element in the Universe. According to the Big Bang Theory, the Universe at beginning expanded and later cooled to form subatomic particles and the simplest elements.
Hydrogen along with some helium and lithium is the first element came into existence in the Universe. Hydrogen is the most abundant element in the Universe; it accounts for almost 73 % to 75 % of all matter in the Universe. Helium is the second most abundant element which is approximately 24 %. Both represent 99 % of the total matter. Oxygen follows helium as the third most abundant element. Then there are traces of other elements like carbon, nitrogen, iron, and many others.
Note: The matter which we are discussing is composed of atoms, but there exist other strange things in the Universe like dark matter, dark energy which comprise of more than 95 % of the Universe.
The Milky Way is the galaxy in which we live. It contains more than 300 billion stars. The composition of the Milky Way is like that of the Universe.
The below graph lists the ten most common elements in the Milky Way.
As we can see from the above graph, hydrogen, helium, and oxygen are the most common element available in our Milky Way. Most of the stars are nothing but a cloud of hydrogen holds by gravitation force. Other elements comprise less than 2 %. Despite the percentage of other elements less than 2 %, they play an important role in astronomical activities.
The Solar System is the planetary system with the Sun at the centre and other objects revolving around it. This 4.568 billion-year-old system comprises of one star (the Sun), 8 known planets (including our Earth), and various other astronomical objects like natural satellites, comets, minor planets.
Since the Solar System is much smaller than the Milky Way, it is more studied, and we have more data on its composition. The graph below presents the element composition of the Solar System.
As we can observe from the above graph, the abundance decreases exponentially with an increase in atomic number. Hydrogen, helium, oxygen, carbon, nitrogen, neon, magnesium, silicon, and iron are the most common elements in the Solar System.
The Sun is the energy source of life on Earth. It is 4.6 billion-year-old. The mass of the Sun is (1.988 × 1030) kg, and it is 333 000 times heavier than the Earth. Three fourths of the Sun’s mass consists of hydrogen and remaining helium. Hydrogen is the fuel of the Sun. Every second, million tons of hydrogen fuses into helium through the process of hydrogen fusion. Further fusion reactions produce lithium, beryllium. Eventually, heavier elements like oxygen, carbon, neon, nitrogen, iron are also formed in the Sun.
The different layers of the Sun contain different composition. The photosphere is of an outer layer of the Sun which radiates light. It comes between the convection zone and the chromosphere as shown in the above figure. The elemental composition by mass in the photosphere is as follows:
|% by mass||73.46||24.85||0.77||0.29||0.16||0.12||0.09||0.07||0.05||0.04|
Since the Sun encompasses more than 99% mass of the Solar System, the elemental composition in both is almost the same. The below graph presents atoms abundance in log10 scale.
Note: There are some differences in the graph of the sun and the solar system. The concentration of lithium in the sun is much less than in the solar system. This is due to lithium in the sun is consumed because of nuclear reactions.
The Earth, the planet of life, is the planet in which we live. It is the third planet in our Solar System. The mass of this 4.5 billion-year-old planet is 5.972 × 1024 kg.
Iron (31.9 %), oxygen (29.7 %), silicon (16.1 %), and magnesium (15.4 %) are the most common elements in the Earth, making 93.1 % of the Earth’s mass. This data is demonstrated in the below pie diagram.
The bar-graph below presents the abundance of elements in the Earth. The y-axis is part per million, ppm (kg⁄kg) of elements in log10 scale. We can see some differences between the figure below and the fgure of the sun. Particularly, the abundance of hydrogen and helium in the Earth is very less in comparison to the Sun. Also, the composition of carbon and nitrogen is also less than in the Sun.
The Earth’s crust is the outermost layer of the Earth. Its thickness varies from 5 km to 80 km and takes less than 1 % volume of the Earth. It formed billions of year ago because of the cooling of the Earth. Elemental composition of Earth’s crust is mentioned in the below table.
|Atomic Number||Elements in Earth Crust||% Mass||% Volume||% Atoms|
As we can see from the above table, oxygen and silicon make more than 70% of the crust. They are followed by aluminium, iron, calcium, sodium, potassium, magnesium. The graph below illustrates the above table.
Apart from the above-mentioned elements, elements found in the crust are titanium (0.62 %), hydrogen (0.14 %), phosphorous (0.13 %), manganese (0.09 %), carbon (0.09 %), barium (0.05 %), chlorine (0.05 %), sulphur (0.05 %), chromium (0.04 %), zirconium (0.03 %), fluorine (0.03 %), and nickel (0.02 %). Other heavier elements exist in traces.
The Earth’s mantle is the second layer between Earth’s core and crust. Its mass is 4.01 × 1024 kg around 67 % of Earth’s mass. It occupies more than 80 % of Earth’s volume. Temperatures inside the mantle can vary from 200 ℃ at the upper surface to 4000 ℃ at the lower surface. At such a high temperature, solid matter exists in the melt state. Thus, the mantle is semi-fluid. The abundance of elements in the mantle present in the below pie diagram.
From the above figure, oxygen, magnesium, silicon, and iron account for 95 % mass of the mantle. We can also observe that percentages of magnesium and iron in the mantle are much more than that of crust.
The core of the Earth is at its centre. It is further divided into inner and outer core. Temperatures inside the core vary from 4000 ℃ to 6000 ℃. It is believed that the inside core is solid while the outer one is liquid. It is mainly composed of iron (85 %) and nickel (5.2 %). Other elements are also present in smaller percentages like silicon (6 %), sulphur (1.9 %), chromium (0.9 %).
The atmosphere of the Earth is a mixture of various gases that we called air. The primary components of air are nitrogen (78.08 %) and oxygen (20.95 %). Other important components are water, argon, carbon dioxide, methane, and ozone. The table below lists it.
|Water*||H2O||0 to 4|
|*gases with variable composition|
Note: In the above table, the percentages of nitrogen and oxygen remain nearly constant but of water, carbon dioxide, methane, nitrous oxide, and ozone vary significantly with location. These gases are greenhouse gases.
The composition of the urban soils varies from cities to cities. Also, the composition changes with time due to man-made activities Typical elements in urban soils are oxygen, silicon, carbon, aluminium, calcium, hydrogen, nitrogen, potassium, iron. The graph below lists average values. The owner of the graph has plotted the below graph by evaluating urban soils from 300 cities in all the five continents.
Seawater is the giant water body on the surface of the Earth that covers about 70 % of the Earth’s surface. The prime component of seawater is water. A molecule of water (H2O) consists of two atoms of hydrogen and one atom of oxygen. So, there is no doubt these two elements (oxygen and hydrogen) will be abundant in oceans. Other main components in oceans are salts. The average salinity of seawater is 3.5 % (35 g L−1). Sodium and chloride ions are predominating ions in oceans.
From the above figure, some of the most common elements in oceans are oxygen (86.0 %), hydrogen (10.8 %), sodium (1.075 %), chlorine (1.857 %), magnesium (0.127 %). The below logarithmic graph presents the concentration (µg L−1) of elements on the y-axis with atomic numbers on the x-axis.
The human body is the most complex and unique structure in the Universe. The average weight of a human is 70 kg; from this 70 kg, more than 45 kg is only water. This is because 65 % of the human body is water. The most common elements in the body are oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorous. These six elements make up 98 % of our body weight.
Oxygen is the present in the highest amount in our body. It accounts for 65 % of the total body mass. Oxygen is found in water. It is a key element in respiration. Carbon follows oxygen; around 18 % of the body is made up of carbon. Carbon occurs in all organic contents: carbohydrates, proteins, fats, and nucleic acids. Hydrogen is the third most common element in the body. The hydrogen concentration in mole term is very high. But because of its lightweight, it ends up to 10 % of the body weight. Nitrogen is present in proteins, nucleic acids, and it amounts 3 % of the total body mass. Our bones and teeth comprise of calcium which is about 1.4 % of the body. There are also many other elements present in our body, but their concentration is very less.
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