Periodic Classification of Elements : In this first part of the SSC Maharashtra Board science textbook, we will cover topics such as the nature of matter, forces, motion, energy, and organisms. By the end of this book, you will have a thorough understanding of the concepts and principles that form the basis of the natural world.
Page No-16 : Periodic Classification of Elements
What are the types of matter?
In terms of composition, matter can be classified into two main categories: pure substances and mixtures. Pure substances can be further divided into elements and compounds. Elements are made up of only one type of atom, while compounds consist of two or more different types of atoms chemically bonded together. Mixtures, on the other hand, are made up of two or more pure substances physically combined together, but not chemically bonded. Mixtures can be further divided into homogeneous mixtures (where the composition is uniform throughout) and heterogeneous mixtures (where the composition is not uniform throughout).
What are the types of elements?
There are currently 118 known elements, which can be classified into several categories based on their properties. One common way to categorize elements is by their states at room temperature:
- Metals: These are elements that are typically solid at room temperature, except for mercury, which is liquid. Metals are known for their malleability, ductility, and conductivity.
- Nonmetals: These are elements that can exist in all three states of matter at room temperature. Non-metals are generally poor conductors of heat and electricity.
- Metalloids: These are elements that have properties that are intermediate between those of metals and nonmetals.
Elements can also be classified into groups based on their electron configurations and chemical properties, including alkali metals, alkaline earth metals, transition metals, halogens, and noble gases.
What are the smallest particles of matter called?
The smallest particles of matter are called atoms. Atoms are the basic building blocks of matter and are composed of protons, neutrons, and electrons. Protons and neutrons are found in the nucleus of the atom, while electrons orbit the nucleus in shells or energy levels. Atoms of different elements have a different number of protons, which is called the atomic number. The arrangement of these particles within the atom determines the chemical and physical properties of the element.
What is the difference between the molecules of elements and compounds
The main difference between molecules of elements and compounds is the composition of their atoms. Elements consist of only one type of atom, so molecules of elements contain only atoms of the same element. For example, a molecule of oxygen (O2) contains two oxygen atoms, both of which are of the same element.
Periodic Classification of Elements : can you recall
Compounds, on the other hand, are composed of two or more different types of atoms that are chemically combined. Molecules of compounds contain atoms of different elements that are bonded together in a specific ratio. For example, a molecule of water (H2O) contains two hydrogen atoms and one oxygen atom, which are bonded together.
Another difference between molecules of elements and compounds is their physical and chemical properties. Molecules of elements have properties that are similar to the properties of that element, while molecules of compounds have properties that are unique to that specific compound.
Identify Dobereiner’s triads from the following groups of elements having similar chemical properties.
Mg (24.3), Ca (40.1), Sr (87.6)
S (32.1), Se (79.0), Te (127.6)
Be (9.0), Mg (24.3), Ca (40.1)
Page No-18– Use Your Brain Power
Chlorine has two isotopes,viz, C1-35 and C1-37.Their atomic masses are 35 and 37 respectively.Their chemical properties are same.Where should these be placed in Mendeleev’s periodic table? In different places or in the same place?
Page No-21–Use your brain power !
Q.How is the problem regarding the position of cobalt (59Co) and nickel (59Ni) in Mendeleev’s periodic table resolved in modern periodic table?
Ans : In Mendeleev’s periodic table, cobalt (59Co) and nickel (59Ni) were placed in different groups despite having similar chemical properties. However, the modern periodic table resolves this issue by placing them in the same group, since they have the same number of valence electrons and similar chemical behavior. This group is called the transition metals group, and it is located in the middle of the periodic table.
How did the position of 13Cl17 and 37Cl17 get fixed in the modern periodic table?
The placement of elements like chlorine (Cl) and chloride (Cl-) in Group 17, also known as Group VIIA or the halogens, is based on their chemical properties and atomic structure.
The modern periodic table organizes elements based on their atomic number, which represents the number of protons in an atom’s nucleus. Chlorine, with an atomic number of 17, falls within the same group as other halogens such as fluorine (F), bromine (Br), iodine (I), and astatine (At).
The group number indicates the number of valence electrons an element possesses, which are the electrons in the outermost energy level of an atom. Elements in Group 17 have 7 valence electrons, making them highly reactive and likely to form ions with a -1 charge, such as chloride (Cl-).
Periodic Classification of Elements : can you recall
This arrangement showcases the periodicity of elements, where elements with similar chemical properties are grouped together. It helps scientists and chemists easily understand and predict the behavior of elements, which is super useful!
Hope that sheds some light on how elements like chlorine and chloride found their fixed spots in the modern periodic table.
Can there be an element with atomic mass 53 or 54 in between the two elements, chromium 52Cr24 and manganese 55Mn25 ?
The element with an atomic mass of 53 or 54 that falls between chromium (24Cr) and manganese (25Mn) is vanadium (23V). Vanadium has an atomic mass of approximately 51. So, there isn’t an element with an atomic mass of exactly 53 or 54 within that specific range, but vanadium does fall in between those two elements.
What do you think? Should hydrogen be placed in the group 17 of halogens or group 1 of alkali metals in the modern periodic table?
While hydrogen does share some similarities with both halogens and alkali metals, it doesn’t quite fit perfectly into either group. Its behavior is rather unique!
However, if we had to choose between the two, the current consensus is that hydrogen is typically placed in group 1 of alkali metals in the modern periodic table. This is because hydrogen can exhibit similar characteristics as alkali metals, such as having a single valence electron and the potential to form positive ions.
Periodic Classification of Elements : can you recall
But remember, the periodic table is constantly evolving as our understanding deepens, so who knows what future revisions may bring? It’s always exciting to see how science progresses!
What are the values of ‘n’ for the shells K, L and M?
The values of ‘n’ for the electron shells K, L, and M are as follows:
- The K shell has a value of n = 1.
- The L shell has a value of n = 2.
- The M shell has a value of n = 3.
What is the maximum number of electrons that can be accommodated in a shell? Write the formula
The formula to calculate the maximum number of electrons that can be accommodated in a shell is 2n², where “n” represents the shell number. For example, the first shell (n = 1) can accommodate a maximum of 2(1)² = 2 electrons, the second shell (n = 2) can accommodate a maximum of 2(2)² = 8 electrons, and so on.
Deduce the maximum electron capacity of the shells K, L and M.
The maximum electron capacity of each shell can be determined using a simple rule known as the “2n^2” rule, where “n” represents the shell number.
For the K shell (n=1), the maximum electron capacity is 2 x (12) = 2 electrons.
and for the L shell (n=2), the maximum electron capacity is 2 x (22) = 8 electrons. For the M shell (n=3), the maximum electron capacity is 2 x (32) = 18 electrons.
It’s important to note that the maximum electron capacity determines the total number of electrons that can occupy each shell, but the actual number of electrons in an atom may be lower depending on its atomic number.
What is the relationship between the electronic configuration of an element and its valency?
he electronic configuration of an element is indeed closely related to its valency. Valency refers to the number of electrons an atom needs to gain, lose, or share in order to achieve a stable, full outer electron shell.
The electronic configuration of an element tells us how its electrons are distributed in different energy levels or shells around the nucleus. The outermost shell, known as the valence shell, is particularly important when determining valency.
SSC-Science-Part-1-Ch-3-Can You Recall
Typically, elements with incomplete valence shells tend to be more reactive as they strive to either gain or lose electrons to achieve a stable configuration. For example, elements in Group 1 of the periodic table, like sodium, have one electron in their outermost shell, so their valency is 1, meaning they tend to lose that electron to achieve a stable configuration.
On the other hand, elements in Group 17, like chlorine, have seven electrons in their valence shell. Their valency is 1 as well, but in the opposite direction—they tend to gain one electron to achieve a stable configuration.
Of course, there are exceptions and variations depending on the element and its position in the periodic table, but understanding the electronic configuration can give us valuable insights into an element’s valency.
The atomic number of beryllium is 4 while that of oxygen is 8. Write down the electronic configuration of the two and deduce their valency from the same.
Let’s start with the electronic configurations of beryllium and oxygen.
The electronic configuration of beryllium (atomic number 4) is 1s² 2s².
On the other hand, the electronic configuration of oxygen (atomic number 8) is 1s² 2s² 2p⁴.
Now, let’s deduce their valencies. Valency is determined by the number of valence electrons, which are the electrons in the outermost shell of an atom.
In the case of beryllium, since it has 2 valence electrons in the 2s orbital, its valency is 2.
For oxygen, it has 6 valence electrons (4 in the 2s orbital and 2 in the 2p orbital), so its valency is also 2.
So, both beryllium and oxygen have a valency of 2.
I hope that helps! Let me know if there’s anything else I can assist you with.
What is the periodic trend in the variation of valency while going from left to right within a period? Explain your answer with reference to period 2 and period 3.
When moving from left to right within a period on the periodic table, there is a periodic trend in the variation of valency. Let’s explore this trend using the examples of period 2 and period 3.
In period 2, which consists of elements from lithium (Li) to neon (Ne), the valency generally increases from 1 to 4. This is because as we move from left to right, the number of valence electrons increases. For example, lithium (Li) has 1 valence electron in the 2s orbital, while neon (Ne) has 8 valence electrons in the 2s and 2p orbitals. So, the valency increases progressively from 1 to 4 across period 2.
Periodic Classification of Elements : can you recall
In period 3, which consists of elements from sodium (Na) to argon (Ar), the trend is similar. The valency generally increases from 1 to 7. As we move from left to right, the number of valence electrons again increases. For instance, sodium (Na) has 1 valence electron in the 3s orbital, while argon (Ar) has 8 valence electrons in the 3s and 3p orbitals. Therefore, the valency increases progressively from 1 to 7 across period 3.
In summary, when moving from left to right within a period, there is an overall increase in the valency of elements. This is due to the increasing number of valence electrons as we move across the period.
What is the periodic trend in the variation of valency while going down a group? Explain your answer with reference to the group 1, group 2 and group 18.
As you go down a group on the periodic table, there is a periodic trend in the variation of valency. Let’s take a closer look at Group 1 (alkali metals), Group 2 (alkaline earth metals), and Group 18 (noble gases) to understand this trend.
Periodic Classification of Elements
In Group 1, the alkali metals, the valency generally increases as you move down the group. This is because the number of valence electrons, which are the electrons in the outermost energy level, increases. As you move down the group, each element gains an additional energy level, resulting in an increased number of valence electrons. For example, lithium (Li) has one valence electron and a valency of 1, while cesium (Cs) has one valence electron in a higher energy level and a valency of 1. So, the valency increases from 1 to 1 as you move down Group 1.
SSC-Science-Part-1-Ch-3-Can You Recall
Similarly, in Group 2, the alkaline earth metals, the valency also increases as you move down the group. However, in this case, the valency is determined by the number of electrons needed to fill the outermost energy level. Elements in Group 2 have two valence electrons, and as you move down the group, the number of energy levels increases. This means that the valency increases by 1 with every step down the group. For instance, beryllium (Be) has a valency of 2, while barium (Ba) has a valency of 2. So, the valency increases from 2 to 2 as you move down Group 2.
Periodic Classification of Elements
On the other hand, Group 18 consists of the noble gases, which have a valency of 0. This is because noble gases have completely filled outermost energy levels, making them stable and unreactive. Since the outermost energy level is already filled, noble gases do not tend to gain or lose electrons to form compounds. Therefore, their valency remains at 0.
So, to summarize the trend, as you move down a group, the valency generally increases in Groups 1 and 2 due to the increase in the number of valence electrons or energy levels. However, in Group 18, the valency remains constant at 0 because noble gases have completely filled outermost energy levels.
Look at the elements of the third period. Classify them
I can do that for you! The third period of the periodic table consists of the elements sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chlorine (Cl), and argon (Ar).
In this period, we have three metals: sodium, magnesium, and aluminum. These elements typically have shiny appearances, good conductivities of heat and electricity, and are malleable and ductile.
The remaining elements in the third period, silicon, phosphorus, sulfur, chlorine, and argon, are nonmetals. Nonmetals generally have dull appearances, poor conductivities of heat and electricity, and are brittle.
On which side of the period are the metals? Left or right
Metals are generally find on the left side of the periodic table. They are know for their lustrous appearance, good conductivity of heat and electricity, and malleability.
On which side of the period did you find the nonmetals?
nonmetals can be finded on the right side of the periodic table. They include elements like oxygen, nitrogen, fluorine, and many others.
What is the cause of nonmetallic character of elements?
The nonmetallic character of elements is actually determine by a few factors. One key factor is the number of valence electrons an element has. Elements with a higher number of valence electrons tend to exhibit more nonmetallic properties.
Another factor is the electronegativity of the element. Electronegativity is a measure of an element’s ability to attract electrons towards itself. Nonmetals generally have higher electronegativities compared to metals, which makes them more likely to form covalent bonds by sharing electrons rather than losing or gaining them completely.
Periodic Classification of Elements
The atomic size also plays a role. Nonmetals tend to have smaller atomic sizes, which means their outer electrons are closer to the nucleus. This makes it easier for them to attract and hold onto electrons, contributing to their nonmetallic behavior.
Overall, the nonmetallic character of elements is a result of a combination of factors like the number of valence electrons, electronegativity, and atomic size. It’s fascinating how these factors influence the unique characteristics of each element!
What is the expected trend in the variation of period?
As you move from left to right across a period in the periodic table, the nonmetallic character generally tends to increase. Nonmetallic character refers to the ability of an element to gain electrons and form negative ions.
In the periodic table, elements on the left side, such as metals, have a lower nonmetallic character. They tend to lose electrons and form positive ions. On the other hand, elements on the right side, closer to the noble gases, have higher nonmetallic character. They have a greater tendency to gain electrons and form negative ions.
SSC-Science-Part-1-Ch-3-Can You Recall
It’s important to note that this trend may have some exceptions due to factors such as atomic structure and electronegativity. But overall, the trend of increasing nonmetallic character from left to right in a period is a useful guideline.
What would be the expected trend in the variation of nonmetallic character of elements down a group?
When it comes to the variation of nonmetallic character of elements down a group, we can generally observe an interesting pattern. As we move down a group on the periodic table, the nonmetallic character tends to increase.
Let me explain it in a more intuitive way! Nonmetallic character refers to how much an element tends to gain or share electrons in a chemical reaction. Elements on the right side of the periodic table, such as oxygen or fluorine, are highly nonmetallic because they have a strong desire to gain electrons.
Periodic Classification of Elements
As we move down a group, the atomic radius tends to increase due to the addition of new electron shells. This increase in atomic radius leads to a decrease in the effective nuclear charge experienced by the valence electrons. Consequently, the valence electrons are less strongly attracted to the nucleus, making it easier for elements to gain or share electrons. This tendency ultimately results in an increase in nonmetallic character as we move down a group.
Of course, there may be exceptions and unique cases, but this general trend holds true for many elements. Isn’t chemistry fascinating?