Table given below shows a part of the periodic table. Using this table explain why Li and Na are considered as active metals.

Both Li and Na are considered active metals because it has one electron in the valence shell. Both Li and Na tend to lose this electron to gain stability. Hence, Li and Na are considered as active metals.

Table given below shows a part of the periodic table. Using this table explain why the atomic size of Mg is less than that of Na.

Magnesium's nuclear charge is higher than the Sodium nuclear charge. Thus, Magnesium is smaller than Sodium by attracting electrons towards it by shrinking its size. On moving from sodium to chlorine in the third period, the atomic number increases, and thereby, the nuclear charge also increases. This leads to a greater attraction of the electrons towards the nucleus, leading to the shrinkage of the atom. Although the number of electrons also increases, each additional electron is placed within the same shell, thus all the electrons being equidistant from the nucleus.

Use Mendeleev's Periodic table to predict the formulae for the oxides of the following elements: K , C , Al , Si

According to Mendeleev's periodic table, the elements K , C , Al , Si are present in group I , IVA , III and IVA respectively. Hence, their oxides will be K 2 O , CO 2 , Al 2 O 3 and SiO 2 .

What were the criteria used by Mendeleev in creating his periodic table?

The criteria used by Mendeleev in creating his Periodic Table are: (i) Elements were arranged in the increasing order of their atomic masses. (ii) All elements in a group should have similar chemical properties. That is, he used the criteria that the element with similar chemical properties should be in the same group.

E M B I B E

Foundation Course Chemistry>Chapter 5 - Periodic Classification Of Elements>EXERCISE>Q 4

EASY

10th CBSE

IMPORTANT

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Potassium, bromine and krypton are elements in period $4$ of the Periodic Table. In which group of the periodic table Krypton can be found?

Important Questions on Periodic Classification Of Elements

EASY

10th CBSE

IMPORTANT

Foundation Course Chemistry>Chapter 5 - Periodic Classification Of Elements>EXERCISE>Q 4

Potassium, bromine and krypton are elements in period $4$ of the Periodic Table.

Bromine exists as a molecule. Draw a 'dot-and-cross' diagram to show the bonding in a molecule of bromine.

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10th CBSE

IMPORTANT

Foundation Course Chemistry>Chapter 5 - Periodic Classification Of Elements>EXERCISE>Q 4

Potassium, bromine and krypton are elements in period $4$ of the Periodic Table.

Krypton does not react with either potassium or bromine. Explain the unreactive nature of krypton.

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10th CBSE

IMPORTANT

Foundation Course Chemistry>Chapter 5 - Periodic Classification Of Elements>EXERCISE>Q 5

An element X has a total of

31

nucleons, out of which

16

are neutrons. Write the electronic configuration of an atom of element X.

MEDIUM

10th CBSE

IMPORTANT

Foundation Course Chemistry>Chapter 5 - Periodic Classification Of Elements>EXERCISE>Q 5

An element X has a total of

31

nucleons, out of which

16

are neutrons. Determine the group and period number of element X.

MEDIUM

10th CBSE

IMPORTANT

Foundation Course Chemistry>Chapter 5 - Periodic Classification Of Elements>EXERCISE>Q 5

An element X has a total of

31

nucleons, out of which

16

are neutrons. Give the formula of the ion formed by element X.

MEDIUM

10th CBSE

IMPORTANT

Foundation Course Chemistry>Chapter 5 - Periodic Classification Of Elements>EXERCISE>Q 6

What physical and chemical properties of elements were used by Mendeleev in creating his periodic table? List two observations which posted a challenge to Mendeleev's periodic law.

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10th CBSE

IMPORTANT

Foundation Course Chemistry>Chapter 5 - Periodic Classification Of Elements>EXERCISE>Q 7

Table given below shows a part of the periodic table.

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