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21 Chemistry -- Classification of Elements and Periodic Table

The table below gives information about the atomic structure of some elements. Elements Protons Electron Arrangement Group in periodic table Metal and Non- metal  A 6 .................. 14 Nonmetal B 19 2,8,8,1 .................. metal C .................. 2,8 18 Nonmetal ...

The table below gives information about the atomic structure of some elements.

Elements
 Protons Electron Arrangement Group in periodic table Metal and Non- metal 
A 6 ..................
 14 Nonmetal
B 19 2,8,8,1
 .................. metal
C .................. 2,8
 18 Nonmetal
D 9 2,7
 17 ..................

a. Fill in the blank spaces in the table.

b. Which of the above elements will react with element D to form an ionic

compound?

c. Which of the above elements exists in a monatomic molecule?

d. Which of the above elements can form a hydrogen bond?

1 Answers

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 a.

Elements
 Protons Electron Arrangement Group in periodic table Metal and Non- metal 
A 6 2,4 14 Nonmetal
B 19 2,8,8,1
 1 metal
C 10 2,8
 18 Nonmetal
D 9 2,7
 17 Nonmetal

b. Ans: Element B (Potassium) will react with the element D (fluorine) to form an ionic compound i.e. Potassium fluoride.

c. Ans: Elements that exist in monoatomic molecules are elements A (carbon), element B (potassium) and element C (Neon). All the elements from above table exists in a monoatomic molecule except element D (fluorine).

d. Ans: Element D (fluorine) having high electronegativity form a hydrogen bond.

More questions on Classification of Elements and Periodic Table

How does electronegativity differ from electron affinity? Arrange the following in the order of increasing electronegativity: M, M-, M+  .

Ans: Electronegativity and electron affinity differs from each other in the following ways:

Electronegativity Electron Affinity
  • It is the tendency of an atom of element to attract bond pairs of electrons towards itself.
  • It is amount of energy released when an isolated gaseous state atom gain an electron.
  • It is applied only to a single atom.
  • It is either applied to an atom or a molecule.
  • Electronegativity is qualitative.
  • It is quantative.

According to increasing electronegativity: M-...

Sodium and Mg+ ion have same number of electrons but removal of electron from Mg+ requires more energy than sodium. Explain. 

Ans: Though sodium andMg+ion have same number of electrons the atomic size of Mg+is smaller than Na. Since, smaller the size, the greater is the nuclear force of attraction for valance electrons due to which removal of electron from Mg+requires more energy than sodium.

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Ans:As we know the elements having half-filled and full filled electronic configuration are stable and they need more energy to move the electron and have higher ionization energy. So, (a) and (c) have higher ionization energy because they have fulfilled and half-filled electronic configuration respectively and (b) has lowest ionization energy due to having unstable electronic configuration.

Size of the cation is smaller than the size of parent atom. Explain.

Ans: Size of cation is smaller than the size of parent atom because as parent atom loses electron and form cation where number of proton becomes more than number of electron and attractive force increases so radius decreases.

Size of the anion is larger than the size of parent atom. Explain.

Ans: The size of anion is larger than the size of parent atom because anions are formed due to gain of electrons. When the electrons increases, there are still the same number of protons. This causes the electrons to not be bound tightly to the nucleus like earlier and results in an increase atomic size.

Electron gain enthalpy of fluorine is unexpectedly less than that of chlorine. Give reason. 

Ans: Fluorine has very small atomic size so there is more inter electronic repulsion. But chlorine has larger size and repulsion between the electron of chlorine is very less. Hence, it can easily gain electron but fluorine can't. So electron gain enthalpy of fluorine is unexpectedly less than of chlorine.

 State modern periodic law. Why is modern table superior to Mendeleev's periodic table?

Ans: Modern periodic law states that, " The physical and chemical properties of elements are the periodic function of their atomic numbers."

Modern periodic table does correct the defects of Mendeleev's Periodic table. It is based on atomic number which is a more fundamental property of the atom. It removes the anomalyabout the position of isotopes in the Mendeleev's periodic table. It also removes the other anomaliesfound in Mendeleev's periodic table like grouping of chemically dissimilar...

A student reported that the radii of Cu, Cu+ and Cu++ are 96 pm, 122 pm and 72 pm respectively. Do you agree with the reported values? Justify the answer.

Ans: No, I don't agree with reported values. The measurement is made wrongly. More the positive charge more will be the nuclear attraction and outermost electron is more attracted towards the nucleus and the atomic radius is less. So Cu++< Cu+< Cu should be the order. But the measurement shows Cu+> Cu > Cu++ which can not be true.

 Electron affinity of alkaline earth metal and noble gases are almost equivalent to zero. why?

Ans: Since alkaline earth metal and noble gases are stable elements due to having full or half filled electronic configuration. So, they can't easily gain any electron. Therefore their electron affinity are almost equivalent to zero.

Define isoelectronic species.

Ans: Isoelectronic species are theatoms or ions that have same number of electrons.


Why the first ionisation energy of sodium is higher than that of magnesium?

Ionisation energy of an element depends on several factors including the atomic size, effective nuclear charge, electronic configuration, penetration of electrons and so on.

But in case of Sodium and magnesium, the first ionisation energy of Sodium is higher because as the atomic size of sodium is comparatively smaller than Magnesium so it experiences strong effective nuclear charge hence, more amount of energy is required to release valence electron in its ground state.

Is there any trend for ions describing either the increasing or decreasing hydration energy ? If yes do explain . 

Which is bigger Li+ or Na+?

SimilarlyLi+would be the smallest because it has only 2 electrons and therefore the least electron- electron repulsion. When comparing F- and Na +, we have to be careful, as both of them have 10 electron,SoNa+is smaller due to thelargerattractive force of the protons.

explain how to solve it.

For the elements with large atomic numbers, we prefer to write the electronic configuration taking the help of inert elements near to that element. And for this, we may need knowledge about every element of the periodic table which is quite difficult.

So in this context, we take the help of half-filled and full filled orbitals. I mean the electronic configuration is done by fulfilling the electrons in the orbitals either fully or half to get a stable configuration. Since f orbital can hold 14...

1.    Name the type of bonds which are present in ice. 2.    Explain O-hydroxy Benz aldehyde and P-hydroxy Benz aldehyde, which is more soluble in water and why?3.    Lone pairs of electrons p...

1.Name the type of bonds which arepresent in ice.

Ans: The type of bond present in ice are:1. Covalent bond2. Hydrogen bond

2.Explain O-hydroxy Benz aldehydeand P-hydroxy Benz aldehyde, which is more soluble in water and why?

Ans: P-hydroxy benzaldehyde is more soluble in water than o-Hydroxy benzaldehyde, because P-Hydroxy benzaldehydecan form hydrogen bonds with water molecules resulting in enhanced solubility.


3. Lone pairs of electrons present onan atom in any molecule affect its geometry....

Electronegativity is a relative concept. Explain.

Electronegativity is a realtive concept. The first reason is that we are studying Pauling's scale of Electronegativity which is developed by taking Fluorine as the most electronegative element and that has a EN value of 4.0.

The other reason is a highly EN element - Chlorine is considered more EN if only it has been paired up with a less EN element. If it has been paired up with element equal or greater in EN value than Chlorine, Chlorine isn't considered EN at that moment.

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